Atrial fibrillation treatment systems and methods

ABSTRACT

Methods for treating cardiac complex rhythm disorder in a patient can include receiving a plurality of electrical signals from a sensor system, wherein each electrical signal corresponds with a separate location on a cardiac wall of the heart of the patient, and wherein each electrical signal comprises an electrogram waveform; and ranking the electrical signals relative to each other based on at least a uniformity and a frequency of the electrogram waveform of each electrical signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S.Provisional Patent Application No. 61/662,323, titled ATRIALFIBRILLATION TREATMENTS, which was filed on Jun. 20, 2012; U.S.Provisional Patent Application No. 61/798,456, titled ATRIALFIBRILLATION TREATMENTS, which was filed on Mar. 15, 2013; and U.S.Provisional Patent Application No. 61/799,242, titled UPSTREAM APPROACHFOR ABLATION OF ATRIAL FIBRILLATION, which was filed on Mar. 15, 2013,the entire contents of each of which are hereby incorporated byreference herein.

BACKGROUND

Atrial fibrillation (“AF”) is a heart disease that affects a significantportion of the population of the United States (e.g., about 1 to 2percent in the general population and up to about 10 percent in elderlypopulations). In a patient with AF, the electrical impulses that arenormally generated by the sinoatrial node are overwhelmed bydisorganized electrical activity in the atrial tissue, leading to anirregular conduction of impulses to the ventricles that generate theheartbeat. The result is an irregular heartbeat, which may beintermittent or continuous. In human populations, AF-induced irregularheartbeat is a significant source of stroke, heart failure, disability,and death.

There are a number of surgical options available for treating AF. Oneapproach is known as the Cox-Maze III procedure. In this procedure, theleft atrial appendage is excised, and a series of incisions and/or cryo-or radiofrequency-lesions are arranged in a maze-like pattern in theatria. The incisions encircle and isolate the pulmonary veins. Theresulting scars block the abnormal electrical pathways, improving normalsignal transmission and restoring regular heart rhythm. Less invasivetechniques are also possible, which may use heating or cooling sourcesto create impulse-blocking lesions on the heart by ablation rather thanincision.

Catheter-based radiofrequency ablation is a particularly commontreatment for symptomatic AF, as it is less invasive than surgery.Whether this, or any of the foregoing treatments is used, however, thereare certain drawbacks and/or limitations with known techniques.Embodiments discussed below can ameliorate, avoid, or resolve one ormore of these drawbacks, as will be apparent from the presentdisclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The written disclosure herein describes illustrative embodiments thatare non-limiting and non-exhaustive. Reference is made to certain ofsuch illustrative embodiments that are depicted in the figures, inwhich:

FIG. 1 is a schematic representation of a left and a right atrium withdisordered electrical pulses emanating from the pulmonary veins, whichmay be described as paroxysmal atrial fibrillation.

FIG. 2 is a schematic representation illustrating an ablative treatmentfor isolating the electrical pulses to resolve the disorder illustratedin FIG. 1.

FIG. 3 is a schematic representation of a left and a right atrium withdisordered electrical pulses emanating from the pulmonary veins and alsoemanating from the atrium wall, or cardiac substrate, which may bedescribed as complex paroxysmal, persistent, or longstanding persistentatrial fibrillation.

FIG. 4 is a schematic representation illustrating an ablative treatmentfor isolating sources of electrical pulses to resolve the cardiaccomplex rhythm disorder illustrated in FIG. 3; in some instances, theablative treatment may be incomplete as drivers of atrial fibrillationmay be missed (e.g., not isolated), depending on their location.

FIG. 5 is a schematic representation of a portion of the cardiacsubstrate, or atrium wall, having multiple atrial drivers that causeatrial fibrillation, particularly more complex types, wherein the atrialdrivers generate wavefronts of electrical impulses; the wavefronts areshown in FIG. 5 at a time soon after formation, and the view of FIG. 5is a schematic enlarged view of a portion of FIG. 3 taken along the viewline 5 shown therein.

FIG. 6 is a schematic representation such as that of FIG. 5 illustratingthe wavefronts at a later time, wherein wavefronts from various atrialdrivers collide with each other, and this collision of wavefronts thatwere initiated by the drivers can lead to complex and fractionatedelectrical wavelets.

FIG. 7 is another schematic representation such as that of FIG. 6, butfurther including anatomical boundaries or scarred regions between themultiple atrial drivers, wherein the wavefronts are shown at a latertime than those in FIG. 5, and wherein FIG. 7 illustrates that theatrial drivers generate primary wavefronts that ultimately collide andinteract with the anatomic boundaries or scars to generate secondarywavefronts, further impacting the complexity and irregularity of theelectrical wavelets.

FIG. 8 is a schematic plot illustrating the electrical signals(point-based assessment of an electrical wave), or waveforms, detectedat two different regions of the cardiac substrate shown in FIG. 7 acrosswhich the primary and/or secondary wavefronts travel, wherein the upperplot illustrates that the signals generated by collision of wavefronts,collision of wavefronts and scars, and/or collision of wavefronts andanatomic boundaries can be more complex and irregular, and wherein thelower plot illustrates that signals from the initial drivers can berapid and relatively regular.

FIG. 9 is a schematic illustration of the left atrium, whereinelectrical signals are detected at a plurality of regions.

FIG. 10 is a plot illustrating the electrical signal waveforms detectedat each of the regions identified in FIG. 9, wherein it can be seen thatthe different waveforms have different frequencies.

FIG. 11 is a schematic representation illustrating the location mappingof atrial drivers found by ranking electrical signals based on theiruniformity and frequency.

FIG. 12 is a schematic representation illustrating an atrial driverisolation procedure to electrically isolate three of the atrial driversrepresented in FIG. 11 so as to prevent undesired signals from thesedrivers from propagating along the atrial wall.

FIG. 13 is a schematic representation illustrating an atrial driverisolation procedure to electrically isolate two of the atrial driversshown in FIG. 11 in a manner slightly different than that shown in FIG.12, and further showing a focal ablation procedure to locally isolate athird atrial driver.

FIG. 14A is a flowchart depicting an illustrative method of treatingatrial fibrillation.

FIG. 14B is a flowchart depicting another illustrative method oftreating atrial fibrillation.

FIG. 14C is a flowchart depicting yet another illustrative method oftreating atrial fibrillation.

FIG. 15 is a schematic diagram of an embodiment of a system that can beused to identify one or more atrial drivers.

FIG. 16 is a schematic view of a portion of the system of FIG. 15 thatincludes a cutaway view of a heart of a patient and a perspective viewof an embodiment of a non-contact multi-array sensor positioned in theright ventricle of the heart.

FIG. 17 is a schematic view, similar to FIG. 16, that includes across-sectional view of a heart of a patient and a perspective view of adepicts a portion of the system of FIG. 15 cross-sectional view of thenon-contact multi-array sensor of FIG. 16 deployed in the left atrium ofthe heart.

FIG. 18 is an enlarged cutaway view of the left atrium of the heart of apatient, similar to FIG. 17, which shows a non-contact multi-arraysensor deployed in the left atrium.

FIG. 19 is a diagram of an illustrative output display from the systemof FIG. 15.

FIG. 20 is an equivalent circuit of a measurement made by the system ofFIG. 15.

FIG. 21 is a diagram of a measurement made by the system of FIG. 15.

FIG. 22 is a display representing the “coherence” measure and the indexof hemodynamic performance as determined by the system of FIG. 15.

FIG. 23 is a schematic representation of a non-contact sensor collectingcardiac signals from multiple regions or volumes and interpolating thesignals to locations on the cardiac substrate or atrial wall.

FIG. 24 is a display representing the cardiac signals, specificallyelectrograms, obtained via an arrangement such as shown in FIG. 23 andtheir identified associated regions on the cardiac substrate or atrialwall.

FIG. 25A is a schematic cross-sectional view of a portion of anotherembodiment of a system for identifying one or more atrial drivers,wherein the system includes a multi-sensor array that is shown in aconstricted or non-deployed state.

FIG. 25B is another schematic cross-sectional view of the portion of thesystem shown in FIG. 25A, wherein the multi-sensor array is in anexpanded or deployed state such that sensors thereof are in contact withthe atrial wall.

FIG. 26 is a schematic cross-sectional view of a portion of anotherembodiment of a system for identifying one or more atrial drivers,wherein the system includes a multi-sensor array that is positioned atan exterior of the patient.

FIGS. 27A-27D depict illustrative instrumentation and methods forobtaining trace electrograms associated with the heart.

FIG. 28 is a schematic representation of an illustrative method by whicha non-contact sensor collects cardiac signals from multiple regions ofthe cardiac substrate or atrial wall.

FIG. 29 is a flowchart depicting an illustrative method of treatingatrial fibrillation.

FIG. 30 is a plot depicting an electrocardiogram of a patient who has asinus rhythm with intermittent suppression by a repetitive slow atrialdriver, along with a simplified electrocardiogram in which only themajor voltage peaks are represented.

FIG. 31 is a plot depicting an example of a sinus rhythmelectrocardiogram, along with a simplified electrocardiogram in whichonly the major voltage peaks are represented.

FIG. 32A is a schematic representation of a portion of a cardiacsubstrate, or atrium wall, having a primary atrial driver that generatesa regular series of wavefronts of electrical impulses that propagatetoward a secondary atrial driver, which may also be referred to as abystander driver, that is suppressed.

FIG. 32B is a schematic plot illustrating the electrical signals(point-based assessment of an electrical wave), or wavefronts orwaveforms, detected at a region of the cardiac substrate designated by ahexagon in FIG. 32A illustrating that the signals generated by thedriver are regular and have a predictable, repeated period.

FIG. 33A is a schematic representation of another portion of a cardiacsubstrate having a primary atrial driver that generates a regular seriesof wavefronts of electrical impulses that propagate toward a secondaryatrial driver, wherein the secondary atrial driver is stable and notsuppressed by the primary driver, and likewise generates a regularseries of wavefronts of electrical impulses that propagate toward theprimary atrial driver, wherein a frequency of the wavefronts produced bythe secondary atrial driver is lower than a frequency of the wavefrontsproduced by the primary atrial driver.

FIG. 33B is a schematic plot illustrating the electrical signals (e.g.,waveforms) detected at a region of the cardiac substrate designated by ahexagon in FIG. 33A illustrating that the signals generated by thedrivers are regular and have a predictable, repeated period and neitherset of waveforms produced by either driver suppresses operation of theother driver.

FIG. 34A is a schematic representation of another portion of a cardiacsubstrate having a primary atrial driver that generates a regular seriesof wavefronts of electrical impulses that propagate toward a secondaryatrial driver, wherein the secondary atrial driver is stable andlikewise generates a regular series of wavefronts of electrical impulsesthat propagate toward the primary atrial driver, wherein a frequency ofthe wavefronts produced by the secondary atrial driver is lower than afrequency of the wavefronts produced by the primary atrial driver, andwherein every third wavefront produced by the secondary atrial driversuppresses what would be every fourth wavefront of the primary driver.

FIG. 34B is a schematic plot illustrating the electrical signals (e.g.,waveforms) detected at a region of the cardiac substrate designated by ahexagon in FIG. 34A demonstrating the periodic suppression of primarywavefronts due to activity of the stable secondary driver.

FIG. 35A is a schematic representation of another portion of a cardiacsubstrate having a primary atrial driver that generates a regular seriesof wavefronts of electrical impulses that propagate toward a secondaryatrial driver, wherein the secondary atrial driver functionsintermittently, and thus the two operational modes of the secondarydriver are designated by alternative scenarios (as indicated by therecitation “OR”); wherein in the upper alternative, the secondary atrialdriver is dormant, and thus the primary atrial driver is permitted togenerate its electrical wavefronts, and in the lower alternative, thesecondary atrial driver is temporarily active and generates a standaloneor irregular wavefront that temporarily suppresses generation of awavefront by the primary driver (which is indicated in the upperalternative by intermittent broken lines where wavefronts would beexpected).

FIG. 35B is a schematic plot illustrating the electrical signals (e.g.,waveforms) detected at a region of the cardiac substrate designated by ahexagon in FIG. 35A illustrating the periodic suppression of primarywavefronts due to activity of the intermittent secondary driver.

FIG. 36 is a schematic depiction of a portion of an illustrative methodfor identifying drivers from a trace electrocardiogram, wherein uniquefrequencies are isolated to identify dominant drivers.

FIG. 37 is a schematic representation of another portion of a cardiacsubstrate having an atrial driver that is spaced from a series of fivedifferent sensors by varying amounts, wherein each sensor is representedby a numbered hexagon.

FIG. 38A is a schematic plot illustrating the electrical signals (e.g.,waveforms) that may be detected by each of the sensors shown in FIG. 37when the atrial driver is a primary driver from which wavefrontsregularly propagate outwardly.

FIG. 38B is a schematic plot illustrating the electrical signals (e.g.,waveforms) that may be detected by each of the sensors shown in FIG. 37when the atrial driver is a secondary driver that has a lower frequencythan a neighboring driver (e.g., a neighboring primary driver) and/orthat generates wavefronts intermittently, such that wavefronts are showninitially propagating outwardly relative to the innermost sensor, butthereafter wavefronts are shown propagating inwardly toward theinnermost sensor.

FIG. 39 is a plan view of an embodiment of a sensor assembly thatincludes multiple contact sensors that can extend along a cardiacsubstrate in at least two orthogonal directions, or stated otherwise, inat least two dimensions, to define at least a two-dimensional sensingarea, wherein the sensor assembly is depicted in operation adjacent to acardiac wall.

FIG. 40 is a plan view of another embodiment of a sensor assembly thatincludes multiple contact sensors that can extend along a cardiacsubstrate in at least two orthogonal directions, or stated otherwise, inat least two dimensions, to define at least a two-dimensional sensingarea, wherein the sensor assembly is depicted in operation adjacent to acardiac wall

FIG. 41 is a flowchart depicting an illustrative method of treatingatrial fibrillation.

FIG. 42 is a flowchart depicting another illustrative method of treatingatrial fibrillation.

FIG. 43 is a plan view of an embodiment of a sensor assembly in theprocess of gathering electrograms from a portion of an atrial wall,wherein a driver is within a sensing region of the sensor assembly.

FIG. 44A is a plot that includes electrograms gathered via the sensorassembly and that also shows a base signal of the heart.

FIG. 44B is a plot that includes the electrograms from FIG. 44A in arearranged format to demonstrate propagation of wavefronts from thedriver.

FIG. 45 is a plan view of an embodiment of a sensor assembly in theprocess of gathering electrograms from a portion of an atrial wall,wherein two separate drivers are within a sensing region of the sensorassembly.

FIG. 46A is a plot that includes electrograms gathered via the sensorassembly and that also shows a base signal of the heart.

FIG. 46B is a plot that includes the electrograms from FIG. 46A in arearranged format to demonstrate propagation of wavefronts from thedrivers.

FIG. 47 is a plan view of an embodiment of a sensor assembly in theprocess of gathering electrograms from a portion of an atrial wall,wherein a driver is external to a sensing region of the sensor assembly.

FIG. 48A is a plot that includes electrograms gathered via the sensorassembly and that also shows a base signal of the heart.

FIG. 48B is a plot that includes the electrograms from FIG. 48A in arearranged format to demonstrate propagation of wavefronts from thedriver.

FIG. 49 is a plan view of an embodiment of a sensor assembly in theprocess of gathering electrograms from a portion of an atrial wall,wherein a first driver is at an exterior of the sensing region of thesensor assembly and a second driver is within the sensing region of thesensor assembly.

FIG. 50A is a plot that includes electrograms gathered via the sensorassembly and that also shows a base signal of the heart.

FIG. 50B is a plot that includes the electrograms from FIG. 50A in arearranged format to demonstrate propagation of wavefronts from thedrivers.

FIG. 51 is a plan view of an embodiment of a sensor assembly in theprocess of gathering electrograms from a portion of an atrial wall,wherein two drivers are near a sensing region of the sensor assembly butneither driver is within the sensing region.

FIG. 52A is a plot that includes electrograms gathered via the sensorassembly and that also shows a base signal of the heart.

FIG. 52B is a plot that includes the electrograms from FIG. 52A in arearranged format to demonstrate propagation of wavefronts from thedriver.

FIG. 53 is a plan view of an embodiment of a sensor assembly in theprocess of gathering electrograms from a portion of an atrial wall,wherein one driver is near a sensing region of the sensor assembly andanother portion of the atrial wall that previously acted as a driver hasbeen ablated and no longer emits wavefronts.

FIG. 54A is a plot that includes electrograms gathered via the sensorassembly and that also shows a base signal of the heart.

FIG. 54B is a plot that includes the electrograms from FIG. 44A in arearranged format to demonstrate propagation of wavefronts from thedriver.

DETAILED DESCRIPTION

As noted above, many procedures for treating AF involve creating apattern of lesions around the pulmonary veins so as to electricallyisolate the pulmonary veins. Further lesion patterns may also be used toblock other errant, irregular, problematic, or otherwise undesiredelectrical signals. The procedures are often quite lengthy and may beprotracted or otherwise complicated when it is difficult to determine alocation on the heart from which the problematic electrical signalsemanate.

Catheter-based radiofrequency ablation is an example of an establishedtreatment for symptomatic AF, and can involve the creation of lesions asjust described. Success rates can vary depending on the AF subtype. Forexample, for paroxysmal AF, a success rate of 70%-85% may be common, asthe disease predominantly involves pulmonary or great vein triggers.Stated otherwise, the high success rate may be achievable because thepulmonary or great vein triggers may be readily isolated by creatingblocking lesions around the pulmonary veins. In contrast, persistent AFand longstanding persistent AF may have a lower success rate (e.g.,4%-60%), as the disease may involve not only primarily venous triggers,but also scars and/or multiple drivers within the left and right atria.As used herein, the term “driver” refers to any location, area, orregion on or in the heart that is a source of AF signals. A driver cancomprise, for example, a focal trigger, a substrate trigger, or aganglion plexus; or stated otherwise, a driver can comprise amalfunctioning autonomic cell bundle. Drivers may also be referred to asfocal drivers.

Disclosed herein are methods, systems, and devices for identifying,locating, and/or treating such drivers (e.g., malfunctioning autonomiccell bundles) to treat AF. In some embodiments, an electrophysiologyapparatus is used to measure electrical activity occurring in a heart ofa patient and/or to visualize the electrical activity and/or informationrelated to the electrical activity. Other or further embodiments includea methodology for mapping the heart so as to identify a driver. Stillfurther embodiments include a methodology for sorting or rankingelectrograms to determine a position of a driver. Some embodimentsinclude treating a patient via ablation at or near an identified driver.Various embodiments increase the effectiveness of AF treatment and/orreduce overtreatment of patients (e.g., by avoiding the creation oflengthy and/or complicated scars).

FIG. 1 is a schematic representation of a left atrium 102 and a rightatrium 104 with disordered electrical pulses emanating from drivers 105,106, 107, 108 (which are schematically represented by starbursts) in thepulmonary veins 115, 116, 117, 118, respectively. FIG. 1 may bedescribed as illustrating paroxysmal atrial fibrillation.

FIG. 2 is a schematic representation illustrating an ablative treatmentfor isolating the electrical pulses to resolve the disorder illustratedin FIG. 1. In particular, a first ablation path 120 surrounds andisolates the drivers 105, 106 and the pulmonary veins 115, 116, and asecond ablation path 122 surrounds and isolates the drivers 107, 108 andthe pulmonary veins 117, 118.

FIG. 3 is a schematic representation of another example of a left atrium102 and a right atrium 104 with disordered electrical pulses emanatingfrom the pulmonary veins 115, 116, 117, 118 and also emanating from theatrium wall 124, or cardiac substrate. In particular, the disorderedelectrical pulses can emanate from multiple drivers 131, 132, 133, 134,135, 136, 137, 138, as well as the drivers 105, 106, 107, 108. FIG. 3may be described as illustrating persistent or longstanding persistentatrial fibrillation.

FIG. 4 is a schematic representation illustrating an ablative treatmentfor isolating sources of electrical pulses to resolve the cardiaccomplex rhythm disorder illustrated in FIG. 3. Ablation paths 120, 122can be formed to isolate the pulmonary veins 115, 116 and 117, 118,respectively, along with their associated drivers 105, 106, 107, 108.One or more additional ablation paths 140, 142, 144 can also be formed.These ablation paths 140, 142, 144 can be used to block problematicelectrical pulses emanating from the drivers 131, 132, 133, 134, 135,136, 137, and 138.

FIGS. 1-4 illustrate principles that are generally known. For example,the ablation paths 120, 122, 140, 142, 144 can be formed in any suitablemanner. Standard ablation treatments may be used, such as limitedpulmonary vein isolation (PVI), wide-area or antral pulmonary veinisolation (APVI), and/or complex fractionated atrial electrogram (CFAE)ablation. FIGS. 5-13, however, illustrate new and/or further approachesfor treating cardiac complex rhythm disorders. FIGS. 5-10 illustrateconcepts for locating problematic drivers on or within the heart, whichcan be treated in manners such as illustrated in FIGS. 12 and 13. Whilethe concepts discussed with respect to FIGS. 5-10 can aid in explaininghow or why certain methods and systems described herein may beeffective, it is to be understood that these concepts are non-limiting.Stated otherwise, the present disclosure—including the disclosure ofmethods and systems for the treatment of AF—is not bound or limited bytheories or explanations relative thereto that are set forth herein.

FIG. 5 is a schematic representation of a portion of the cardiacsubstrate 150, or atrium wall, having multiple atrial drivers 133, 134,135, 136 that each generates multiple wavefronts of electrical impulses.Wavefronts 153,154, 155, 156 are depicted as circles of a largerdiameter, and additional wavefronts generated thereafter, which aredepicted as circles at the interior of the wavefronts 153, 154, 155,156. The drivers 133, 134, 135, 136 can cause atrial fibrillation, andthe atrial wall can transmit the errant, erroneous, or irregular signalin the same manner that they conduct regular or desirable signals. Thewavefronts detected via the electrograms can be used to identify thepositions at which the undesired signals originate. In FIG. 5, thewavefronts 153, 154, 155, 156 are shown at a time soon after formation.The drivers 133, 134, 135, 136 can each be repetitive, each continuallyinitiating stable wavefronts. Stated otherwise, the drivers 133, 134,135, 136 may be stable so as to regularly generate electrical waveformsthat propagate outwardly and that have stable or substantially constantperiodicities.

FIG. 6 is a schematic representation of a portion of the cardiacsubstrate 150, such as that of FIG. 5, illustrating the wavefronts 153,154, 155, 156 at a later time. The wavefronts 153, 154, 155, 156 fromcorresponding atrial drivers 133, 134, 135, 136 collide with each other.As a result, portions of the cardiac substrate 150 positioned betweenthe drivers 133, 134, 135, 136 encounter complex electrical signals. Thesignals may be noisy, and may be sporadic or irregular, as wavefrontsfrom the multiple atrial drivers 133, 134, 135, 136 may arrive withirregular and/or offset timing.

FIG. 7 illustrates a different cardiac substrate 150′ that includesanatomical boundaries and/or damaged tissue 161, 162, 163 (e.g., scarredregions, such as from prior ablative procedures and/or degenerativeheart ailment), which may more generally be referred to as boundarystructures, between the multiple atrial drivers 133, 134, 135, 136. Theprimary wavefronts 153, 154, 155, 156 generated by the drivers 133, 134,135, 136 can ultimately collide and interact with the boundarystructures 161, 162, 163 to yield secondary wavefronts. For example,secondary wavefronts 166, 167 may result from interaction of a primarywavefront, which is generated by the driver 133, with the boundarystructure 161. As a result, portions of the cardiac substrate 150′positioned between the drivers 133, 134, 135, 136 encounter complexelectrical signals. The signals may be noisy, and may be sporadic orirregular, as wavefronts from the multiple atrial drivers 133, 134, 135,136, as well as from the boundary structures 161, 162, 163 may arrivewith irregular and/or offset timing.

Three regions or positions 170, 171, 175 in the cardiac substrate 150′are shown in FIG. 7. The positions are schematically represented byhexagons, although the regions may not necessarily be hexagonal inshape. The electrical signals encountered at the positions 170, 171 areillustrated in FIG. 8.

In particular, FIG. 8 is a schematic plot 172 illustrating the voltage Vof the electrical signals, or waveforms, as a function of time, asdetected at the positions 170, 171 of the cardiac substrate 150′.Although the waveforms are depicted with discrete pulses (e.g., showinga point-based assessment of an electrical wave), in other instances, thewaveforms appear more wavelike (e.g., such as shown in FIG. 24). As canbe appreciated from the plot that corresponds to the position 170,complex fractionated electrograms can be associated with regions ofmarked electrical variability. Stated otherwise, marked activationshifts can represent collisions of waveforms at a position that isremote from one or more drivers. Accordingly, more complex and/orirregular waveforms can be associated with regions that are remote fromone or more drivers. As can be appreciated from the plot thatcorresponds to the position 171, waveforms that are stable (e.g.,relatively regular) and that are rapid (e.g., have a high frequency) canbe associated with regions that are at or near a driver.

FIG. 9 is a schematic illustration of the left atrium 102, whereinelectrical signals are detected at a plurality of positions 180, 181,182, 183, 184, 185. Any suitable system and/or device may be used todetect the signals at the plurality of positions. More or fewerpositions may be detected than the six shown and/or the detections maybe simultaneous. In other or further instances, detection of electricalsignals at each of the positions may be carried out individually or ingroups, such as by passing a sensor over one or more of the positions ata time.

Illustrative examples of sensing systems and devices that are suitablefor detecting the electrical signals the correspond with the positions180, 181, 182, 183, 184, 185 are discussed further below. For example,in some embodiments, a sensor, which may also be referred to as a sensorsystem or a or a sensor array, can be positioned within the left atrium102. An illustrative example of such a sensor array is shown in FIGS.16-18. The sensor array may be spaced from the inner atrial wall and maybe capable of substantially simultaneously mapping electrical properties(e.g., electrogram waveforms) at numerous regions of the left atrium102. The sensor array may similarly be positioned with the right atrium104 to detect electrical signals corresponding to positions along theinner atrial wall of the right atrium 104. In some instances, the samesensor array is used in either atrium 102, 104, whereas in otherembodiments, multiple sensor arrays may be used. The one or more sensorarrays may collect data from both atria 102, 104 simultaneously, or theymay collect the data serially.

In other or further embodiments, a sensor system, such as one or more ofthe sensor arrays depicted in FIGS. 25A and 25B, may be positioned atthe interior of the left atrium 102 and/or the right atrium 104, and thesensor system may include multiple sensors that are placed in contactwith the inner atrial walls. The sensors may be configured to detectelectrical signals conducted along the wall of the cardiac substrateover time (e.g., electrogram waveforms) at the portions of the atrialwall with which they are in contact.

In still other or further embodiments, electrical signals correspondingwith a various portions of the cardiac substrate, such as the pluralityof positions 180, 181, 182, 183, 184, 185 of FIG. 9, may be obtained viaa sensor system having one or more sensors positioned at an exteriorsurface of the heart and/or protruding into a wall of the heart. Forexample, in some embodiments, one or more sensors may be positionedwithin the body of the patient and/or external to chambers of the heart.

In other or further embodiments, electrical signals corresponding with avarious portions of the cardiac substrate, such as the plurality ofpositions 180, 181, 182, 183, 184, 185 of FIG. 9, may be obtained via asensor system positioned at an exterior of the patient, such as at theskin surface of the patient. One illustrative example of such a sensorsystem is depicted in FIG. 26. The sensor system may include skinelectrodes or any other suitable sensor device or devices, and datacollection via the sensors can include body surface mapping.

In still further instances, more localized sensing may be achieved viasensors such as those depicted in FIGS. 39, 40, and 43. For example, invarious instances, a sensor may be positioned at the end of a catheter(e.g., a steering catheter), which may be positioned within an atriumadjacent to the cardiac wall. In some instances, the sensor may be heldin place for a time sufficient to observe and/or obtain a suitablereading of the electrical activity of the portion of the heart againstwhich the sensor is pressed (e.g., a fraction of a second, severalseconds, a minute or less), and the sensor may then be swept orotherwise relocated to other portions of the heart.

As can be appreciated from the foregoing, any suitable sensor system,which may include one or more sensing devices, can be used to obtainelectrical signals that are associated with various positions on theheart, such as the positions 180, 181, 182, 183, 184, 185 on the leftatrium 102, as shown in FIG. 9. The electrical signals may correspondwith or otherwise be representative of electrical signals conductedalong the wall of the cardiac substrate over time (e.g., electrogramwaveforms). However, in some embodiments, the electrical signals mayinclude data from which electrogram waveforms can be determined. Statedotherwise, the electrical signals may include electrogram waveforminformation, and the electrogram waveforms may be determined from thisinformation. In various embodiments, suitable sensor systems forobtaining electrogram waveform information include one or more of asensor array balloon, a basket mapping catheter and/or any other type ofmapping catheter, and an expandable mesh catheter (each of which may bepositioned within the heart of the patient) and skin electrodes (whichmay be positioned at an exterior of the patient).

FIG. 10 is a plot 188 illustrating the electrical signal waveformsdetected at each of the regions 180, 181, 182, 183, 184, 185 identifiedin FIG. 9. The different waveforms can have different frequencies. Inthe illustrated embodiment, all of the waveforms are generally stable,with regular periodicities. It can be visually ascertained that thewaveform associated with the position 180 has the highest frequency(shortest period), and thus, of all of the regions 180, 181, 182, 183,184, 185, the region 180 may be the closest to, or most likely tocorrespond with, a driver.

As previously noted, all of the waveforms in FIG. 10 are generallystable or periodic. In other instances, one or more of the waveforms maybe complex and/or irregular. In some methods for determining a locationof a driver, the complex and/or irregular waveforms can be eliminated ordiscounted as potential driver positions.

Any suitable method for analyzing and/or ranking waveforms may be usedto identify one or more driver positions. For example, in someembodiments, waveforms can be ranked, as to their likelihood ofcorresponding to a driver position, based on their complexity (or lackthereof) and/or their frequency. Some methods rank the waveforms basedon both a complexity score and/or frequency. In some embodiments,complexity may be determined via Fourier analysis (e.g., Fast FourierTransform (FFT) analysis). A complexity score may be assigned based onthe number of and/or some other property related to the constituentwaves of the complex waveform. In some embodiments, high complexity andlow frequency yield low rankings, whereas low complexity and highfrequency yield high rankings. Rankings may be achieved via a weightingalgorithm. For example, high frequencies and/or low complexities may beweighted higher than low frequencies and/or high complexities.

In other or further embodiments, one or more other factors may beincorporated into the ranking of potential driver sites. For example, insome instances, it may be assumed that multiple driver sites are presentif there are multiple positions that yield high rankings, and if thesepositions are spaced from each other. This assumption may be evenstronger if there are lower-ranked positions that are physicallysituated between the highly ranked positions. For example, thelower-ranked positions may have more complex waveforms than thoseassociated with the highly ranked positions. By way of illustration,with reference again to FIG. 7, the positions 171 and 175 may be morelikely to be at or near drivers (i.e., the drivers 135, 134,respectively), since these positions 171, 175 yield regular waveformswith relatively high frequencies. In some ranking or sorting algorithms,the likelihood that one or more of the positions 171, 175 may be at ornear drivers may be augmented by the fact that the position 170 issituated between them and yields a complex waveform (as depicted in FIG.8). Accordingly, in some embodiments, a ranking algorithm may assignadditional weight to potential driver positions if lower-ranked areasare physically situated between the driver positions. In other orfurther embodiments, waveform amplitude may be used as a parameter inthe ranking criteria. However, in some instances and/or for some sensingsystems, amplitude may be a less useful ranking criteria as amplitudecan be affected by poor electrical contact with the heart tissue. Invarious embodiments, one or more, two or more, or three or more ofwaveform unity, frequency, amplitude, and position (e.g., the positionon the heart with which the waveform is associated) may be used asparameters in the ranking criteria. As discussed further below, otherwaveform criteria may also be used to rank signals as to their proximityto a driver and/or to determine whether signals are likely to haveoriginated from the same or different drivers. For example, in someembodiments, a shape of the waveform, such as whether a slope thereof isinitially positive or negative, the sharpness and/or number of peaks orvalleys, etc., can be used to distinguish signals that originate fromdifferent drivers.

Any suitable algorithms may be used to rank the waveforms and theirassociated positions for likelihood of association with a driver. Insome embodiments, the algorithms may be implemented by a practitioner,such as by visually observing or reviewing electrograms. Theelectrograms, for example, may be provided side-by-side on a display,and the practitioner might observe one or more properties of thewaveforms to determine that a position on the heart associated with oneor more of the waveforms is in proximity to a driver. In other orfurther embodiments, the algorithms may be implemented by a computerand/or dedicated hardware. In general, at least some portions of thesubject matter disclosed herein may be described herein in terms ofvarious functional components and processing steps. A skilled artisanwill appreciate that such components and steps may be implemented as anynumber of hardware or software components or combination thereofconfigured to perform the specified functions. For example, an exemplaryembodiment may employ various graphical user interfaces, softwarecomponents, and database functionality.

For the sake of brevity, conventional techniques for computing, dataentry, data storage, networking, and/or the like may not be described indetail herein. Furthermore, the connecting lines shown in variousfigures contained herein (e.g., FIG. 15) are intended to representexemplary functional relationships and/or communicative, logical, and/orphysical couplings between various elements. A skilled artisan willappreciate, however, that many alternative or additional functionalrelationships or physical connections may be present in a practicalimplementation of a system or method for treating AF.

Additionally, principles of the present disclosure may be reflected in acomputer program product on a computer-readable storage medium havingcomputer-readable program code means embodied in the storage medium. Anysuitable tangible, nontransitory computer-readable storage medium may beutilized, including magnetic storage devices (hard disks, floppy disks,and the like), optical storage devices (CD-ROMs, DVDs, Blu-Ray discs,and the like), flash memory, and/or the like. These computer programinstructions may be loaded onto a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine, such that the instructions that execute on thecomputer or other programmable data processing apparatus create meansfor implementing the functions specified. These computer programinstructions may also be stored in a computer-readable memory that candirect a computer or other programmable data processing apparatus tofunction in a particular manner, such that the instructions stored inthe computer-readable memory produce an article of manufacture includingimplementing means which implement the function specified. The computerprogram instructions may also be loaded onto a computer or otherprogrammable data processing apparatus to cause a series of operationalsteps to be performed on the computer or other programmable apparatus toproduce a computer-implemented process, such that the instructions whichexecute on the computer or other programmable apparatus provide stepsfor implementing the functions specified.

FIG. 11 is a schematic representation illustrating the location mappingof atrial drivers found by ranking electrical signals based on theiruniformity and frequency. In some embodiments, FIG. 11 may correspondwith a display 190 on which a representative image 191 of the heart isdisplayed to a practitioner. The representative image 191 may simulate a3-dimensional model of the heart, or a portion thereof. For example,3-dimensional mapping may be performed. In some embodiments, thepotential driver positions 192 p, 193 p, 194 p, 195 p may be shown onthe display 190. In some embodiments, the rank or weight of each driverposition 192 p, 193 p, 194 p, 195 p may also be shown, such as by color,grayscale, or any other suitable visual indicator. In some embodiments,the representative image 191 may be multicolored, with the color scalecorresponding to driver ranking or likelihood of driver position. Forexample, the image 191 may comprise an isochronal map of at least aportion of the heart. As colored, the representative image 191 mayprovide a 4-dimensional map of the heart, with the three physicaldimensions being overlaid with one or more colors representative of thefourth dimension (such as driver ranking, likelihood of driver position,signal frequency, etc.). In some embodiments, the coloring may bedetermined by one or more of waveform stability and frequency for agiven position on the heart. Accordingly, a practitioner may be able toreadily identify the positions that are likely associated with drivers,such as by looking for one or more “hot spots” on the image 191 and/orone or more positions that are flagged as being potential driverpositions. In further embodiments, the waveforms generated at multiplepositions may also be shown on the display 190 (e.g., in a mannersimilar to that illustrated in FIG. 24). In some embodiments, apractitioner may edit the image 191, such as by adding a desired color,symbol, and/or other indicator at one or more positions on the image 191to indicate any desired property, such as likelihood of being (or beingnear) a driver. In other or further embodiments, a computer program orother machine-implemented algorithm may automatically assign one or morecolors, symbols, and/or other indicators to the image 191.

In some embodiments, atrial electrograms (such as shown in FIGS. 10 and24) can be collected in real time and an isochronal mapping of the heartbased on the electrograms (such as shown in FIG. 11) can be provided.For example, the image 191 may be provided on a screen that isobservable to a practitioner. As further discussed below, in someembodiments, the mapping is achieved via non-contact sensors within theheart. In other embodiments, the mapping may be achieve via contactsensors, certain of which may be moved relative to the surface of theheart. Any other suitable method for mapping the heart and/or obtainingthe image 191 is contemplated. In some arrangements, rapid collection ofhigh density electrograms from the left and right atria is possible.Sorting or ranking algorithms can be used on the electrograms, such asdiscussed above. Signals can be assessed based on stability—for example,non-stable electrograms may be omitted or discounted, whereas stableelectrograms (e.g., those with regular atrial-beat-to-atrial-beat[“A-A”] intervals) may be compared. Local A-A intervals may be assessedand compared. One or more targets may be identified for ablation basedon the most rapid (highest frequency) stable signal or signals.

As can be appreciated from FIG. 11, in some embodiments, multiple AFdrivers can be identified simultaneously. For example, the algorithmsused to analyze and rank, sort, characterize, weight, or otherwiseassign value to waveforms can do so in a way that accounts for thepossibility that multiple drivers may be present. In FIG. 11, fourpotential driver positions 192 p, 193 p, 194 p, 195 p have beenidentified.

FIG. 12 is a schematic representation illustrating an atrial driverisolation procedure to electrically isolate three of the actual atrialdrivers 193 a, 194 a, 195 a, which are representatively shown in FIG.11, so as to prevent undesired signals from these drivers frompropagating along the atrial wall. Ablation paths 120, 122 may besimilar to those shown in FIG. 2. For example, standard PVI proceduresmay be employed. The actual driver 192 a, however, can be addressed in amanner different from what is shown with respect to the driver 131 inFIG. 4. For example, in many instances of prior art techniques, theadditional paths 140, 142 and/or 144 of FIG. 4 may be formed in otherprocedures because an exact location of the drivers 131, 132, 133, 134,135, 136, 137 and/or 138 could not be determined. However, bydetermining the exact or approximate position of the actual driver 192a, focal ablation at, on, or near the driver 192 a is possible, as shownin FIG. 13.

FIG. 13 is a schematic representation illustrating an atrial driverisolation procedure to electrically isolate two of the atrial drivers194 a, 195 a shown in FIG. 11 in a manner slightly different than thatshown in FIG. 12, and further showing a focal ablation procedure tolocally isolate the atrial driver 192 a (of FIG. 12). In FIG. 13, theatrial path 120 is the same as shown in FIG. 12. However, a differentablation path 123 may be formed to isolate the drivers 194 a, 195 a. Thepath 123 may be smaller (or larger) than the path 122 and more focused,or informed, to ensure that the drivers 194 a, 195 a are isolated withinthe PVI ablation path. This can reduce the amount of scarring of theheart wall. The focal ablation 125 can also result in much less damageto the heart than would be possible if the location of the driver 192 awere unknown. As can be appreciated from FIG. 13, electrical isolationof the driver 192 a via ablation can in some instances involve directablation of the driver itself, rather than encircling the driver withscar tissue.

FIGS. 14A-14C are flowcharts depicting illustrative methods 200, 240,260 of treating atrial fibrillation. Some of the stages shown in eachchart may be performed by a practitioner; others may be performed viadevices and/or systems described herein. For example, in some instances,at least some of the steps may be performed via a computing device. Instill further embodiments, at least some of the steps may be automated.Accordingly, any suitable subset of the stages shown in any of FIGS.14A-14C can stand alone as a separate or independent method. Moreover,any suitable order of the depicted stages is contemplated.

With reference to FIG. 14A, the method 200 includes a stage 202 at whichat least a portion of the heart is mapped to determine the electricalisolation of one or more pulmonary veins. At decision block 204, it isdetermined from the mapping whether the one or more pulmonary veins areelectrically isolated from the atrium wall. If not, then the methodproceeds to stage 206 at which the pulmonary veins are isolated from theatrium wall via ablation. If they are isolated, then the method proceedsto stage 208. At stage 208, multiple trace electrograms of the atriumwall are generated using a sensor, or stated otherwise, via any suitablesensor system. Examples of suitable sensor systems are discussed abovewith respect to FIG. 9, and further examples are discussed below withrespect to FIGS. 15-26, 39, 40, and 43. In many embodiments, the sensorsystem is positioned within the heart of the patient to obtain the dataused in the electrograms, although other or further sensor systems mayemploy detection devices that are situated at an exterior of thepatient. At stage 210, the electrogram traces are ranked according totheir uniformity (regularity, lack of complexity, etc.) and/or theirfrequency. As a result of stage 210, the position(s) on the heart thatare associated with the highest ranking electragram trace(s) can beidentified. These identified positions are the target sites at whichdrivers are likely to be (or be near). In other or further methods, theranking can be based on other or further criteria, such as previouslydiscussed. The identification may include tagging, marking, coloring, orotherwise altering an image of the heart, such as the image 191discussed above.

At stage 212, focal ablation is performed at a target site, or ablationlines are created to isolate the target site associated with an atrialdriver. At decision block 214, it is determined whether atrialfibrillation has changed with the treatment thus far. If not (or if ithas changed, but there are still atrial fibrillation issues), then theprocedure loops back to stage 212. If so, then the procedure proceeds todecision block 218, at which it is determined whether atrialfibrillation has been fully resolved. If not, then the procedureproceeds to decision block 220 at which it is determined whether aremapping event should take place. If not, then the procedure loops backto stage 216. If so, then the procedure loops back to stage 208. If theatrial fibrillation has been fully resolved, then the procedure is at anend.

FIG. 14B is a flowchart depicting another illustrative method 240 oftreating atrial fibrillation. The method 240 closely resembles themethod 200. However, the stages 202, 206, and the decision block 204 areomitted. Accordingly, the method 240 proceeds without isolating thepulmonary veins and/or verifying that the pulmonary veins areelectrically isolated. In some instances, the method 240 cansuccessfully resolve AF without isolating the pulmonary veins. Themethod 240 can identify and electrically isolate only the drivers thatare the source of the AF. Otherwise, the stages and decision blocks 208,210, 212, 214, 216, 218 of the method 240 can proceed in the same manneras discussed above with respect to the method 200.

FIG. 14C is a flowchart depicting another illustrative method 260 oftreating atrial fibrillation. At stage 208, multiple trace electrogramsof the atrium wall are generated using a sensor (or sensor system—e.g.,any suitable sensor system, such as those discussed above and below). Atstage 262, each electrogram is mapped to a physical location on theatrium wall, such as by generating or modeling a 3-D representation ofthe atrium wall. Each electrogram may be associated with specificlocations on a model or image of the atrium wall thus generated. Atstage 210, the electrogram traces are ranked according to theiruniformity (regularity/lack of complexity/etc.) and/or their frequency.As a result of stage 210, the position(s) on the heart that areassociated with the highest ranking electragram trace(s) can beidentified. These identified positions are the target sites at whichdrivers are likely to be (or be near). In other or further methods, theranking can be based on other or further criteria, such as previouslydiscussed. In some embodiments, a representation of some property of theelectrogram is assigned to the 3-D model. For example, each electrogrammay be represented by a color, grayscale shade, or other suitable visualindicator corresponding with a property of the electrogram, such as itsfrequency, stability, and/or uniformity, or its ranking or weighting asa potential driver location (which may be calculated or evaluated in anysuitable manner, such as discussed above). Stage 210 can includeoverlaying the 3-D map with a representation of a fourth dimension. Atstage 264, an ablation treatment is planned to electrically isolate thetarget sites. The ablation treatment may include directly ablatingand/or encircling with ablated tissue one or more of the atrial drivers.

In some instances, stage 264 may be omitted, or it may be automatic. Forexample, in some embodiments, the ranking at stage 210 may includeassigning various threshold values to potential ablation sites. Forexample, a likelihood that a position on the atrium wall is at or near adriver may be assigned a color. At stage 210, two or more, three ormore, or four or more colors may be used to rank various positions onthe atrium wall within a like number of probability ranges. For example,three colors may be used to identify highly likely, moderately likely,or unlikely driver positions (e.g., yellow, blue, red, respectively). Incertain of such procedures, the stage 264 may be omitted, or it may beautomatic. For example, the ablation treatment plan at stage 264 maymerely be to perform focal ablation at each position that is marked inthe “highly likely” color (e.g., yellow).

At stage 266, the sensor is removed from the patient. At stage 268, theablation is performed.

FIGS. 15-22 illustrate a non-limiting embodiment of a system 305, andnon-limiting embodiments of components thereof, that can be used in,with, or as one or more of the methods and systems previously discussed.The system 305 can include a non-contacting sensor array that isconfigured to be positioned within the heart and to obtain measurementsat positions that are spaced from the wall the heart.

FIG. 15 is a schematic diagram of the system 305, which can be usedidentifying one or more atrial drivers. The system 305 may be referredto as an electrophysiology mapping system. In some embodiments, thesystem 305 may comprise the EnSite® system available from St. JudeMedical of St. Paul, Minn. In some embodiments, the EnSite® systempresents electrophysiologic data on a static geometry of the heart, andit should be recognized that certain heart information (e.g., EPactivation) is available on a single beat basis. Further examples ofsystems that may be used are provided in U.S. Pat. Nos. 6,978,168;7,187,973; and 7,189,208, the entire contents of which are herebyincorporated by reference herein. Certain of these patents providedetails for receiving cardiac signals (e.g., electrogram) that representelectrical signal transmission along the cardiac wall. Stated otherwise,details are provided for mapping multiple points of electrogram data tophysical regions on the cardiac substrate, which can be accomplished viasensors such as described below.

In the illustrated system 305, a patient 310 is undergoing a minimallyinvasive ablation procedure. The initial stages of the procedure involvemapping the heart and obtaining trace electrograms, as describedhereafter. A specialized catheter 314, which in some arrangements may bea branded EnSite Array™ catheter, is coupled to a breakout box 312. Aconventional electrophysiology catheter 316 may also be introduced intothe patient while a variety of surface electrodes 311 are used tomonitor cardiac activity during the procedure. The breakout box 312permits the ECG cables and EP system to be coupled to additionalhardware, which is not shown in this figure. The patient interface unit318 couples the catheter 314 to a workstation computer 320 and itsrelated peripherals. The workstation operates under the control of asoftware program, which provides a substantial amount of information tothe attending physician.

In use, the physician will see a map image similar to that shown in FIG.19 on a monitor 323. A computed index 351 may also been shown to thephysician as indicated by index value “0.93” seen on the monitor 323,although in other instances the computed index 351 may not be shown. Inother or further instances, trace electrograms may be shown on themonitor 323 (such as depicted in FIG. 24). In general, the physician isable to visualize the intracardiac cavity 332 containing the catheter314, as seen in FIG. 19, on the monitor 323, which may be in color.Color can be used to reduce the clutter in the image. Expressed ordisplayed on this wire frame geometry image 350 are maps and otherelectrophysiology information derived from the catheter 314. In someprocedures, a patient is also provided with one or more pacing catheters324 which are coupled to a temporary pacer 326 through the breakout box312. The temporary pacer 326 allows the physician to make measurementswhile varying the A-V delay and the V-V delay time. Pacing rate may bevaried to ensure capture.

Turning to FIG. 16, the heart 330 is shown schematically with a rightventricle 332 containing the catheter 314 and a conventional EP catheter316 as well as the pacemaker lead 324. In brief, software running on theworkstation 320 in FIG. 15 can create an electrophysiological map of theheart during a single heartbeat as follows. In operation current sourcedfrom a pair of electrodes (electrode 340 and 342) and injected into theheart chamber 332. A roving catheter, shown as EP catheter 316, islocated on the endocardial surface 331 toward the exterior of the heartthis catheter may be moved widely and may be placed on the interiorheart surface along the septum is shown by reference numeral 333. Theinjected current is detected through the electrode 344 on the EPcatheter 316. This location is determined and as the catheter is movedabout the chamber, complete chamber geometry can be built up by notingthe sequential positions of the electrode 344. Incorporated referencesdescribe this process in more detail, but for purposes of thisdisclosure, a convex hull modeling technique is used to build astatically displayed interior geometry of the heart chamber by selectingcertain locations developed from the electrode motion. The convex hullmodel of the interior chamber of the heart can be smoothed and arepresentative wire grid displayed to the physician. Such a wire grid isshown in FIG. 19 as element 350.

The catheter 314 also carries an array of passive electrode sites, whichmay also be referred to a sensors, typified by electrode site 346. Theseelectrodes are arrayed around the geometric access of the balloon 347.At any given instant some of these electrode sites are pointed towardthe exterior surface wall 331 and the septal wall 333. By computing theinverse solution, the electrophysiologic potentials passing along thesesurfaces can be measured within one beat. Reference may be had to U.S.Pat. Nos. 5,297,549; 5,311,866; 6,240,307 and 5,553,611 for furtherdiscussion of the inverse solution and the creation of theelectrophysiologic map. Each of these references is incorporated in itsentirety in the present application.

In some systems, the depolarization wavefront is displayed on arepresentative geometric surface such as the grid surface 350 of FIG.19. The workstation 320 animates this electrophysiology data and thepropagation of the electrical wavefront along the interior surfaces ofthe heart can be monitored. Wavefronts 380, 382, and 383 are sequencemovements of the stimulus from pacing site 384 seen in FIG. 19.

FIG. 20 shows an equivalent circuit implementation to facilitate adescription of conduction volumetry measurements made from a catheter314. Returning to the geometry of the array on the catheter 314 theinterior of the balloon 347 is non-conductive which provides a limitedfield of view for each of the electrode sites on the surface of theballoon. In essence each electrode responds only to electrical activitybounded by the heart wall, which is directly opposite the electrodesite. For example, an electrode such as electrode 346 sees electricalactivity and conductance data bounded by the wall 331 and is blind toelectrical activity on wall 333. In a similar fashion, an electrode suchas electrode 350 sees only electrical activity occurring on wall surface333. By monitoring the voltages on the array electrodes during thepulse, or more particularly measuring the resistance between adjacentcolumnar pairs of electrodes as indicated by exemplary differenceamplifier 386 it is possible to compute the volume of a partial slice388 of the chamber volume best seen in FIG. 21. It is important to notethat the volume measurement is segmented into several local volumestypified by volume 388.

FIG. 21 shows a slice of chamber volume computed by measuring thedifference in resistance between electrodes adjacent along the axis 321.This view shows that the volume segments are non-overlapping and extendalong the axis 321. The conductance term R is the resistance measured atelectrodes in the passive array. This value is directly available to thesoftware in the program, and Rho is the conductance of the blood inohms-centimeters. D represents the distance between adjacent electrodesites in the passive array along the axis 321. This value is known fromthe geometry of the catheter 314. The preferred conduction volumetryalgorithms can be computed very fast and the volume changes throughout asingle beat of the heart may be tracked. The measurement of chambervolume is most accurate at the mid volume level indicated in FIG. 20 atreference 390. It is preferred but not required to sum or stack theindependent volume measurements to create “columnar values” centered onthe axis 321. This is achieved by adding volumes 392 through 396 tocreate a column volume 390 located near the septum. A similar process isrepeated to create a column volume near the wall 331 as shown as a slice388 in FIG. 21 as well as elsewhere around the chamber.

Without being bound by theory, it is believed that the most effectiveheartbeat will involve the simultaneous and progressive activation ofall of the muscle tissue, which should result in a self similarreduction in the measured volume among all of the volume segmentsmeasured.

FIG. 22 is a display of four representative volume segments of the heartchamber displayed as a function of time. Eight volumes may usedeffectively in some arrangements. Segment 388 may correspond to theantero-lateral volume while the other traces represent other volumessuch as the septal; antero-septal; anterior; antero-lateral; lateral orother volumes defined around axis 321. A suitable way to compare theself-similarity of the volume waveforms is to cross correlate themstatistically. By cross correlation of the values of the segment volumesover time one can compute a number that represents the similarityrelationship of the various waveforms to each other.

The system 305 may be used for generating trace electrograms. Forexample, in some embodiments the system 305 is not used in placement ofa pacing lead, but rather is used primarily to generate data that isused in identifying atrial drivers. For example, in some embodiments,the contraction efficiency is not calculated or otherwise determinedover the course of a procedure.

As shown in FIGS. 16-19, the catheter 314 may be used in mapping theright and left atria. As shown in FIG. 23, the catheter 14 is insertedinto the left atrium 102, and the balloon 347 and sensors 346 aredeployed. The sensors 346 are capable of obtaining information fromwhich trace electrograms can be generated. For example, the traceelectrograms shown in FIG. 24 can correspond with the positions 411,412, 413, 414, 415, 416, 417, 418, 419 on the atrial wall shown in FIG.23. These trace electrograms can be used in manners such as describedabove.

FIG. 25A is a schematic cross-sectional view of a portion of anotherembodiment of a system for identifying one or more atrial drivers,wherein the system includes a multi-sensor array 450 that is shown in aconstricted or non-deployed state within the left atrium 102.

FIG. 25B is another schematic cross-sectional view of the portion of thesystem shown in FIG. 25A, wherein the multi-sensor array 450 is in anexpanded or deployed state such that sensors 452 thereof are in contactwith the atrial wall. Each sensor 452 may be configured to detectelectrical properties of the atrial wall, from which a trace electrogramcan be generated. Accordingly, a trace electrogram can be generated foreach portion of the wall that a sensor 452 contacts. Further algorithmsmay be possible for generating trace electrograms associated withpositions of the atrial wall that are between the sensors 452. Any ofthe foregoing electrograms thus generated can be employed in any of themethods described above.

FIG. 26 is a schematic cross-sectional view of a portion of anotherembodiment of a system 470 for identifying one or more atrial drivers.The system 470 includes a sensor system 472, which includes a pluralityof sensor devices 474 that are positioned at an exterior of the patient310. In particular, in the illustrated embodiment, the sensor devices474 are skin electrodes. Any suitable number and/or arrangement of skinelectrodes may be used, and these may be situated in an array. Thesensor system 472 can further include, or be coupled with, a processor476, which can store and/or process data received from the sensordevices 474. Information received from the sensor devices 474 can beused in any suitable manner to generate trace electrograms associatedwith positions of the atrial wall of the heart 330. For example,suitable methods for obtaining trace electrograms associated with theheart, based on information from the surface of the body (e.g., frombody surface mapping), are disclosed in U.S. Pat. Nos. 7,016,719 and7,983,743, the entire contents of which are hereby incorporated byreference herein. Schematic diagrams and flow charts associated withsome suitable methods, which are discussed in U.S. Pat. No. 7,983,743,are provided in FIGS. 27A-27D. In some embodiments, a geometrydetermining device, such as a CT scanner, is used to determine thegeometry of the heart 330 and/or the patient's torso. This informationcan be combined with the electrical signal information obtained via thesensor system 472 to map the atrial wall of the heart 330, as well asobtain trace electrograms. The electrograms thus obtained can beemployed in any of the methods described above.

It will be understood by those having skill in the art that changes maybe made to the details of the above-described embodiments withoutdeparting from the underlying principles presented herein. For example,any suitable combination of various embodiments, or the featuresthereof, is contemplated.

FIG. 28 is a schematic representation of an illustrative method by whicha non-contact sensor collects cardiac signals from multiple regions ofthe cardiac substrate or atrial wall. In particular, a non-contactsensing system in which a sensor array is inserted within a chamber ofthe heart but does not contact the wall of the heart, such as the systemdepicted in and described with respect to FIGS. 15-24, can be used inthe method. A portion of the atrial wall 650 is shown. The sensor array(e.g., the balloon or basket with multiple sensors, such as that used inthe EnSite® array) can project potentials to the atrial wall 650 in amanner such as shown in FIG. 21. Each sensor may project the potentialsover an area 671, 672, 673, 674 of the atrial wall 650, such that eacharea 671, 672, 673, 674 represents a sensed wall region. A center pointof each projected potential is shown at the diamonds 661, 662, 663, 664,which may also be referred to as the projected potentials. As can beseen in FIG. 28, the projected potentials may overlap one another. Thesensor potentials can be the average of the wall potential sensedthrough a blood volume, such as depicted in FIG. 21.

The projected potentials can be used to estimate the actual potentialsat the atrial wall 650. Various positions at which potential estimationsmay be provided are depicted as hexagons, such as the estimatedpotential regions 681, 682, 683, etc. For each position, the estimatedpotential may be obtained by interpolating the projected potentials 671,672, 673, 674.

Electrocardiograms of the wall region 650 may be obtained from theinterpolated or estimated potentials 681, 682, 683, etc. Theelectrocardiograms may be evaluated, processed, manipulated, or used inany suitable manner to identify a location of a driver 630. Methods forusing such electrocardiograms to identify the positions of the drivers630 are discussed above (e.g., in FIGS. 14A-14C) and below. Following isthe discussion of another method for identifying the position of adriver 630 and treating AF.

FIG. 29 is a flowchart depicting a method of treating AF. At stage 702,potentials of the wall region 650 are measured and collected over aperiod of time (e.g., in the form of one or more electrocardiograms).The measurements may be made via a plurality of sensors that extend inat least two dimensions. For example, as shown in FIG. 21, theillustrated sensor array can include four sensors that are coplanar. Insome embodiments, the sensors may be extend in three dimensions.

At stage 704, potentials are projected onto the wall 650. The wall 650may be spatially mapped. At stage 706, potentials at a plurality ofchamber wall regions (e.g., the regions 681, 682, 683) are estimated byinterpolating projected potentials. At stage 708, electrograms areestimated at the plurality of chamber wall regions. At stage 710, theestimated electrograms are ranked to identify target sites of atrialdrivers. Suitable ranking algorithms are discussed above, and caninclude weighting of the electrograms based on their uniformity and/orfrequency. Other ranking factors may include amplitude, wave shape, etc.The target sites thus identified may subsequently be targeted andablated (e.g., focal ablation).

FIG. 30 is a plot 800 depicting an electrocardiogram of a patient whohas a normal sinus rhythm and a simplified representation of theelectrocardiogram. In particular, the upper curve 802 depicts a traceelectrocardiogram that may be obtained in any suitable manner, includingany of the various methodologies disclosed herein, whether bynon-contact or contact sensors within the heart or other sensors outsideof the heart (e.g., at the skin of a patient). In some embodiments,sensors such as described above with respect to 23, 25A, 25B, and 26 maybe used. In other or further embodiments, sensors such as describedbelow with respect to FIGS. 39, 40, and 43 may be used.

The lower curve 804 depicts a simplified version of theelectrocardiogram, wherein only the major voltage peaks are represented.Such simplified versions of waveforms will be used in additional plotshereafter. Accordingly, it should be understood that in many instances,although plots merely showing discrete peaks may be illustrated in someof the drawings, the plots in fact have more complicated waveforms whenmeasured by any of a variety of types of sensing equipment.

FIG. 31 is a plot 850 depicting an electrocardiogram of a sinus rhythmwith intermittent suppression by a repetitive slow atrial driver. Theupper curve 852 shows the voltage readout as a function of time as itmay actually be perceived by a sensor, whereas the lower curve 854 is asimplified version of the electrocardiogram in which only the majorvoltage peaks are represented, such as discussed above.

FIG. 32A is a schematic representation of a portion of a cardiacsubstrate 950, or atrium wall, having a primary atrial driver 931 thatgenerates a regular series of wavefronts 951, 952, 953, 954, 955, 956 ofelectrical impulses that propagate toward a secondary atrial driver 932,which may also be referred to as a bystander driver that is suppressed.The secondary driver 932 may be suppressed by dominant signals receivedfrom the primary driver 931 in the same way that occasional primarydriver signals may be suppressed by neighboring drivers (which isdiscussed below with respect to FIGS. 34A and 34B). The secondary driver932 is depicted in FIG. 32A as not generating any wavefronts thatpropagate toward the primary driver 931 due to suppression from theprimary driver 931. The primary driver 931 can be a rapid, repetitivefocal point or focal region of the cardiac substrate that initiates theelectrical wavefronts. Without being limited by theory, primary drivers931 may be found at or embodied in pulmonary veins, extra pulmonaryveins, ectopic sites, scar borders, ganglions, and/or anatomicboundaries.

Any suitable sensor or sensor array may be used to detect electricalsignals at the region 980, which is depicted as a hexagon, although thedetection region need not in actuality be hexagonal. In FIG. 32A, theregion 980 is concentric with the primary driver 931 for ease in thepresent discussion. Similar concentric arrangements are also disclosedin subsequent drawings. Accordingly, a sensor may be positioned todetect a wavefront as it is generated or soon after it is generated.Such an arrangement can simplify the present discussion and analysis.However, it should be understood that in various methods of detectingdrivers, the sensors may be positioned at a distance from the drivers,but algorithms such as discussed herein can be used to locate the driverbased on information gathered from multiple sensors. Accordingly, somesensors that can obtain electrical data from multiple portions of theatrial wall simultaneously can be useful in identifying the location ofdrivers.

FIG. 32B is a schematic plot 990 illustrating the electrical signals(point-based assessment of an electrical wave), or waveforms, detectedat the region 980 of the cardiac substrate. The signals wavefronts 951,952, 953, 954, 955, 956 are represented as discrete pulses of voltage.In the illustrated embodiment, the wavefronts 951, 952, 953, 954, 955,956 have a predictable, repeated period and a consistent amplitude. Thepresence of the primary driver 931 at or near the region 980 could bereadily determined from a plot such as the plot 990. For example, in amethod of treating AF, such as those described above and below, theelectrogram associated with the plot 990 could be evaluated relative toelectrograms obtained from neighboring regions to determine that theregion 980 is at or near a driver (i.e., the driver 931). Theregularity, frequency, and/or other properties of the wavefronts 951,952, 953, 954, 955, 956, as compared with the same properties ofwavefronts obtained from neighboring regions, can be used in identifyingthe region 980 as a likely candidate for the location of a primarydriver.

FIG. 33A is a schematic representation of another portion of a cardiacsubstrate 1050 having a primary atrial driver 1031 that generates aregular series of wavefronts 1051, 1052, 1053, 1054, 1055 of electricalimpulses that propagate toward a secondary atrial driver 1032. In theillustrated arrangement, the secondary atrial driver 1032 is stable andlikewise generates a regular series of wavefronts 1071, 1072, 1073 ofelectrical impulses that propagate toward the primary atrial driver1031. In the illustrated embodiment, the secondary driver 1032 isoriented near a boundary 1060, such as an anatomical boundary, damagedtissue, non-conducting cardiac tissue, and/or a scar. In this scenario,both drivers 1031, 1032 persist due to the boundary 1060. That is, theboundary 1060 does not allow the more rapidly firing primary driver 1031to suppress the slower secondary driver 1032. Accordingly, although afrequency of the wavefronts produced by the secondary atrial driver islower than a frequency of the wavefronts produced by the primary atrialdriver, the boundary 1060 between the two drivers 1031, 1032 allows thesecondary driver 1032 to not be suppressed by the wavefronts 1051, 1052,1053, 1054, 1055 and thus generate its own wavefronts 1071, 1072, 1073.In other scenarios, the distance between the primary driver 1031 andsecondary driver 1032, the organization of the propagating wavesinitiated by the secondary driver 1032, and/or the frequency andamplitude of the secondary wavefronts may prevent the secondarywavefronts from suppressing the primary driver 1031.

FIG. 33B is a schematic plot 1090 illustrating the electrical signals(e.g., waveforms) detected at a region 1080 of the cardiac substrate1050 designated by a hexagon in FIG. 33A. The plot 1090 illustrates thatthe signals generated by each of the primary and secondary drivers 1031,1032 are regular and have a predictable, repeated period. Moreover,neither set of waveforms 1051, 1052, 1053, 1054, 1055; 1071, 1072, 1073produced by either driver suppresses operation of the other driver 1032,1031.

FIG. 34A is a schematic representation of another portion of a cardiacsubstrate 1150 having a primary atrial driver 1131 that generates aregular series of wavefronts 1152, 1153, 1154, 1156, 1157 of electricalimpulses that propagate toward a secondary atrial driver 1132. Thesecondary atrial driver 1132 is stable and likewise generates a regularseries of wavefronts 1171, 1172, 1173, 1174, 1175, 1176 of electricalimpulses that propagate toward the primary atrial driver 1131. Afrequency of the wavefronts produced by the secondary atrial driver 1132is lower than a frequency of the wavefronts produced by the primaryatrial driver 1131. Certain electrical wavefronts of the secondarydriver 1132 can occasionally suppress wavefront generation by theprimary driver 1131, typically at predictable intervals. In particular,in the illustrated embodiment, every third wavefront produced by thesecondary atrial driver 1132 suppresses what would be every fourthwavefront (i.e., 1151, 1155) of the primary driver 1131. In thisscenario, there is irregularity of the rapid primary driver 1131 due tointermittent suppression from the secondary driver 1132 at a lowerfrequency that penetrates the primary driver 1131 due to penetration ofthe secondary wavefronts into the region of the primary driver 1131 attimes shortly after electrical tissue recovery in the region of theprimary driver 1131.

Without being limited by theory, suppression, such as just discussed, isa natural phenomenon of cardiac tissue. The tissue can conduct anelectrical signal, but then it is transiently dormant while it acquiresan inward charge. Accordingly, in situations such as described abovewith respect to FIG. 34A, whether an electrical signal from the primarydriver 1131 or from the secondary driver 1132 will be propagated by thecardiac tissue in the region of the primary driver 1131 can result fromwhichever waveform hits that region first. Typically, a fast primarydriver 1131 will send signals out so quickly that it will suppress alltissue around it. However, in some instances, if the primary driver 1131does not generate wavefronts quickly enough, another neighboring regioncan be released from its dormant state and conduct its own electricalsignal. If that region starts a wavefront and it reaches the firstregion just as the first region recovers and begins the process ofstarting its own wavefront, the first region (e.g., the region of theprimary driver 1131) will be suppressed before it can activate its ownwavefront. Wavefronts from neighboring, regular drivers can have thesame suppressive effects.

For slow drivers, suppression can be common. For example, for somedrivers, the sinus node/pacemaker cells may only initiate an impulseevery approximately 0.6 to 1.0 seconds, on average. Since cardiac tissuegenerally recovers within about 150 to about 200 milliseconds, any beatthat begins at about 210 to about 600 milliseconds after the sinus beatwill get into the sinus node and suppress it so it does not give off thenext beat. This phenomenon is depicted in FIG. 31.

In the context of abnormal tissues, driver regions that generate orconduct impulses at high frequencies (e.g., with a period of less thanabout 150 milliseconds) may be difficult to suppress, even transiently.Without being bound by theory, this is a reason that certain methods oftreating AF discussed herein (e.g., the methods in FIGS. 14A-14C) caninclude steps, stages, and/or algorithms for identifying drivers byregions that have a dominant and/or rapid signal frequency (e.g.,algorithms in which uniformity and/or frequency value are weighted, withhigher uniformity and higher frequencies indicating stronger likelihoodof driver presence). Given that the heart has anatomic boundaries,random triggers that try to send off their own signals at differentfrequencies, and varied distances between drivers, in some instances,signals from a dominant driver may occasionally be suppressed.Accordingly, additional methods of treating AF can include more ordifferent steps, stages, and/or algorithms for identifying dominantdrivers where occasional suppression is present.

FIG. 34B is a schematic plot 1190 illustrating the electrical signals(e.g., waveforms) detected at a region 1180 of the cardiac substrate1150 designated by a hexagon in FIG. 34A. The plot 1190 demonstrates theperiodic suppression of primary wavefronts due to activity of the stablesecondary driver. For example, where wavefronts 1151, 1155 from theprimary driver 1131 would be expected, only smaller wavefronts from thesecondary driver 1132 are present. As discussed further below, certainmethods for identifying primary or dominant drivers can take intoaccount such occasional wavefront suppression.

FIG. 35A is a schematic representation of another portion of a cardiacsubstrate 1250 having a primary atrial driver 1231 that generates aregular series of wavefronts 1252, 1253, 1254, 1256 of electricalimpulses that propagate toward a secondary atrial driver 1232. Thesecondary atrial driver 1232 functions intermittently, and thus the twooperational modes of the secondary driver are designated by alternativescenarios (as indicated by the recitation “OR”). In the first or upperalternative, the secondary atrial driver 1232 is dormant, and thus theprimary atrial driver 1231 is permitted to generate its electricalwavefronts at a persistent regular frequency. In the second or loweralternative, however, the secondary atrial driver 1232 is temporarilyactive and generates irregular wavefronts 1271, 1272 that temporarilysuppress generation of a wavefront by the primary driver 1231. Thisintermittent suppression is depicted in the upper alternative byintermittent broken lines where wavefronts 1251, 1255 would be expected.Also, the secondary driver 1232 may be temporarily suppressed byincoming wavefronts initiated by the primary driver 1231 causing theinitiation of wavefronts from the secondary driver to be muted. If aperiod of time between wavefronts initiated by the primary driveroccurs, the secondary driver may initiate a wavefront towards theprimary driver 1231.

FIG. 35B is a schematic plot illustrating the electrical signals (e.g.,waveforms) detected at a region 1280 of the cardiac substrate 1250designated by a hexagon in FIG. 35A. The periodic suppression of theprimary wavefronts 1251, 1255 due to activity of the intermittentsecondary driver 1232 is indicated by occasional signals that vary instrength and/or time (e.g., the signals may be slightly earlier thanwould otherwise be expected, which may result in suppression) from theotherwise regular pattern of signals from the primary driver 1231.

FIG. 36 is a schematic illustration of a portion of a method 1300 foridentifying multiple drivers from a trace electrocardiogram. The method1300 can include obtaining the trace electrocardiogram 1305 in anysuitable manner, which is depicted at stage 1310. The electrocardiogram1305 may be obtained, for example, via any of the sensors and sensorsystems described herein, including contact sensors, non-contactsensors, and/or sensors positioned at an exterior of a patient. At stage1320, unique frequencies from the electrocardiogram 1305 are isolatedand dominant drivers are identified. Although these activities aredepicted as occurring in a single step in FIG. 36, in some embodiments,the isolation of unique frequencies and the identification of dominantdrivers may be carried out in distinct steps. Isolation of the dominantfrequencies may be performed in any suitable manner, such as, forexample, via a Fourrier transform and/or any other suitable algorithm.Identification of dominant drivers may involve identifying a specificregion on a three-dimensional map of the heart that is responsible for adominant frequency. Mapping of the heart and correlation of a signalsource to a specific region of the resultant map may be performed in anysuitable manner, such as, for example, any methodology discussed above.One or more portions of the isolation and/or identification steps may beperformed via a computer or computer program. FIG. 36 includes aschematic plot 1330, which may be a byproduct of and/or an intermediateresult of stage 1320. In particular, the plot 1330 shows provides avisual representation of two unique frequencies, depicted as an uppersegment 1332 and a lower segment 1334, that have been isolated from theelectrocardiogram 1305. In some instances, the upper segment 1334, withits higher frequency and greater amplitude, may be identified as (oridentified as being associated with or being at or near) a primarydriver.

FIG. 37 is a schematic representation of another portion of a cardiacsubstrate 1450 having an atrial driver 1433 that is spaced from a seriesof five different sensors 1481, 1482, 1483, 1484, 1485 (or sensedregions, such as the regions 681, 682, 683 in FIG. 28) by varyingamounts. Each sensor or sensed region is schematically represented by anumbered hexagon, although the region sensed may not, in fact, behexagonal. Moreover, it may be desirable merely to sense at variousdistances from the driver 1433, and not necessarily in a straight line.The distances are represented by broken-lined concentric circles.Accordingly, although in the illustrated arrangement, the sensors 1481,1482, 1483, 1484, 1485 are arranged in a straight line, the signalssensed thereby that originate at the driver 1433 will generally be thesame at any point along the circle associated with that sensor. However,signals that originate at positions that are spaced from the driver 1433will appear at different times along each circle. As can be appreciatedfrom the foregoing, in order to locate an atrial driver 1433,particularly where the position of the atrial driver 1433 is not knownfrom the outset, it can be advantageous to have sensors so as to cover amulti-dimensional surface of the wall 1450, rather than merely aone-dimensional line along the wall 1450. For example, a series ofsensors may desirably be placed on the wall in two dimensions, such thatthey cover an area when viewed in a plan view. In further embodiments,the sensors may further follow a three-dimensional contour of the wall1450. Non-contact sensors such as described above can obtainmeasurements in three-dimensions in this manner. Contact sensors such asshown in FIGS. 25A and 25B may also provide such three-dimensional data.Additional contact sensors that are suitable for obtaining suchmeasurements are described below with respect to FIGS. 39, 40, and 43.

FIG. 38A is a schematic plot 1492 illustrating the electrical signals(e.g., waveforms) that may be detected by each of the sensors 1481,1482, 1483, 1484, 1485 when the atrial driver 1433 is a primary driverfrom which wavefronts regularly propagate outwardly. For example, asignal or wavefront 1401 may first be detected by the sensor 1481, thenby the sensor 1482, then by the sensor 1483, then by the sensor 1484,and finally by the sensor 1485. The wavefront 1401 thus may clearlypropagate in a direction away from the driver 1433. The same is alsotrue of a subsequently generated wavefront 1402.

FIG. 38B is a schematic plot 1494 illustrating the electrical signals(e.g., waveforms) that may be detected by each of the sensors 1481,1482, 1483, 1484, 1485 when the atrial driver 1433 is instead asecondary driver that has a lower frequency than a neighboring driver(e.g., a neighboring primary driver) and/or that generates wavefrontsintermittently. Accordingly, the secondary driver 1433 may be subject tosignal suppression, such as discussed above. Due to the secondary, orless dominant nature of the atrial driver 1433 (as may result, forexample, from the driver 1433 having a lower frequency), wavefronts maygenerally propagate toward the secondary driver 1433, rather than awayfrom it. For example, in the illustrated plot 1494, the driver 1433 mayoccasionally generate a wavefront, such as the wavefront 1403. Thiswavefront 1403 may start to propagate outwardly from the driver 1433, asshown by the later detection of the wavefront 1403 by the sensor 1482.However, by the time the wavefront 1403 reaches the position of thethird sensor 1483, a different wavefront 1404 from some other source(e.g., a neighboring primary driver) may have already triggered thecardiac tissue in regions external to the circle associated with thesensor 1482. Indeed, the wavefront 1404 was previously sensed by thesensor 1484, and was sensed prior to that by the sensor 1485.Accordingly, the sensors 1485, 1484, 1483 are shown as having detectedthe wavefront 1404 propagating toward the driver 1433. The wavefront1404 does not further trigger the cardiac tissue in the regions aboutthe sensors 1482 and 1481 in the illustrated arrangement, however, sincethe wavefront 1403 has already triggered the cardiac tissue and it hasnot yet recovered.

Moreover, before the slower-operating driver 1433 is able to generateanother wavefront of its own, it is triggered by another wavefront 1405that originated elsewhere (e.g., at the neighboring primary driver).This wavefront 1405 is shown in the plot 1494 as propagating toward thedriver 1433, given that wavefront 1405 was first detected by theoutermost sensor 1485, and was then detected by the progressively moreinwardly positioned sensors 1484, 1483, 1482, and then 1481.

In view of the foregoing, it may be said that the driver 1433occasionally initiates wavefronts that propagate outwardly. However,wavefronts predominantly propagate inwardly toward the driver. Theproperty of wavefronts generally propagating outwardly from primarydrivers and propagating inwardly toward secondary drivers may be used inlocating primary drivers, such as in the methods described below withrespect to FIGS. 41 and 42.

FIG. 39 is a plan view of an embodiment of a sensor assembly 1500 thatmay be useful in obtaining measurements regarding wavefront propagation,among other wavefront and/or waveform properties. The sensor assembly1500 can include an array of sensors 1502 that extend in at least twoorthogonal directions, or two dimensions (e.g., in the X- andY-directions of the illustrated planar view). The sensors 1502 mayextend in a third direction as well (e.g., in the Z-direction into/outof the page, in the illustrated view) to readily conform to athree-dimensional contour of a heart wall 1550. Each sensor 1502 may becapable of detecting electrical potentials of a region 1580 of the heatwall 1550. The sensors 1502 may define a multi-dimensional(2-dimensional or 3-dimensional) sensing area. In some embodiments, thesensor assembly 1500 may operate in a unipolar mode, e.g., in which eachsensor 1502 detects a potential relative to a common voltage. In otheror further embodiments, the sensor assembly 1500 may operate in abipolar mode, e.g., in which potential differences between adjacent setsof sensors 1502 are detected.

In the illustrated embodiment, the sensor assembly 1500 includes apositioning catheter 1506 that can be used to dynamically change aposition of the sensor array. In some applications, the sensor 1500 ispositioned on the substrate 1550 for a period of time that atrialfibrillation is observed (e.g., over multiple heart beats), and infurther applications, electrogram data can be acquired simultaneouslywith near field and/or far field electrogram data. Methodologies, suchas those disclosed above and below, can be used to identify potentialatrial drivers and portions of the sensed area can be recorded oridentified as potential treatment targets. The sensor 1500 may then berelocated to a new portion of the substrate 1550. In some embodiments,the sensor assembly 1500 can provide a more detailed view of a smallerportion of the cardiac wall 1550 than may be obtained with certainembodiments of the sensor depicted in FIGS. 25A-25B.

The sensor assembly 1500 can further include a support structure 1504,such as a wire or narrower catheter, to which the sensors 1502 aremounted. In the illustrated embodiment, the support structure 1504defines a single branch that is spiraled. In some embodiments, thesupport structure 1504 may be resiliently flexible, and may have aspringing action. For example, in the illustrated embodiment, thesupport structure 1504 may be capable of concave or convex deformationsrelative to a center point of the spiral, which may aid in following acontour of the heart wall. As previously mentioned, the sensor array maybe particularly useful in detecting the direction of propagation ofwavefronts relative to a driver 1530, as depicted by the broken arrows.

In some embodiments, the sensor assembly 1500 can comprise a ReflexionHD™ High Density Mapping Catheter, which is available from St. JudeMedical of Little Canada, Minn.

FIG. 40 is a plan view of another embodiment of a sensor assembly 1600that includes multiple contact sensors 1602 that can extend along acardiac substrate 1650 in at least two orthogonal directions, or statedotherwise, in at least two dimensions, to define at least atwo-dimensional sensing area. Like the sensor assembly 1500, the sensorassembly 1600 may also be configured to extend in three dimensions tofollow a contour of the heart wall 1650. In various embodiments, thesensor assembly 1600 may be operated in a unipolar and/or in a bipolarmode.

Each sensor 1602 of the assembly 1600 may be capable of detectingelectrical potentials of a region 1680 of the heat wall 1650. Thesensors 1602 may define a multi-dimensional (2-dimensional or3-dimensional) sensing area. In the illustrated embodiment, the sensorassembly 1600 includes a positioning catheter 1606 that can be used todynamically change a position of the sensor array. In some embodiments,the sensor assembly 1600 can provide a more detailed view of a smallerportion of the cardiac wall 1650 than may be obtained with certainembodiments of the sensor depicted in FIGS. 25A-25B. The sensor assembly1600 can further include a support structure 1604, such as one or morewires or narrower catheters, to which the sensors 1602 are mounted. Inthe illustrated embodiment, the support structure 1604 defines fivebranches that extend from a distal end of the positioning catheter 1606.In some embodiments, the support structures 1604 may be resilientlyflexible, and may have a springing action. The sensor array may beparticularly useful in detecting the direction of propagation ofwavefronts relative to a driver 1630, as depicted by the broken arrows.

In some embodiments, the sensor assembly 1600 can comprise a PentaRay®NAV Catheter, which is available from Biosense Webster® of Diamond Bar,Calif.

FIG. 41 is a flowchart depicting a method of treating atrialfibrillation 1700. The method can exploit the properties of driversdiscussed herein to aid in identifying probable or actual positions ofthose drivers and subsequently ablating (e.g., focal ablating) thedrivers.

At stage 1702, local electrograms are acquired from a cardiac substrate.The local electrograms may be acquired in any suitable manner, such asdiscussed herein. For example, in some embodiments, non-contact sensorarrays may be used. In other embodiments, sensor arrays (e.g., asprovided by the sensor assemblies 1500, 1600) may be used.

At stage 1704, it is determined whether any local electrograms havestable frequencies. If the determination is affirmative, the methodcontinues on to stage 1706, if not, the process progresses to stage1742.

At stage 1706, it is determined whether the local electrogram, or aseries of local electrograms (e.g., such as described above with respectto FIGS. 38A and 38B) show a propagation of an electrical wavefront. Inparticular, it is determined whether an electrical wavefront is shownpredominantly propagating in a single outward direction, or outwardlyfrom a region. If the determination is affirmative, then the processcontinues to stage 1708. If, however, the determination is negative, orif the wavefronts predominantly propagate in a direction toward a givenregion, then the process continues to stage 1720. The determination atstage 1706 may include comparison of different electrograms. Forexample, all electrograms may be compared with one another, and physicallocations of the heart that are associated with each electrogram may betaken into consideration to determine in what direction an electricalwavefront propagates.

At stage 1708, a local electrogram is identified as a probable atrialdriver. Stated otherwise, a position of the heart wall that isresponsible for generation of the electrogram having the properties thatled to the arrival at stage 1708 is identified as a position at which aprimary driver is likely to be located. For example, a three-dimensionalimage or model of the heart (e.g., the image 191 discussed above) may bemarked with a color or other indicator to identify the potential driver.

At stage 1710, the probable atrial driver electrograms are ranked todetermine which electrogram is most likely to be associated with anatrial driver. In some ranking algorithms, an electrogram is more likelyto be associated with an atrial driver if a propagating signal, or peakvoltage, occurred there earlier than it did in other electrograms.Stated otherwise, in some processes, early occurrences of a propagatingpeak are given a greater weight in a weighting algorithm, or areotherwise assigned higher likelihood that an atrial driver is associatedwith the electrogram. The position of earliest occurrence can yield themost likely position of the driver, in some algorithms.

Other factors may be evaluated instead of, or in addition to, peakpropagation at this stage. For example, frequency, stability, waveformshape, and/or other wave properties, such as those discussed above, maybe evaluated. In some instances, the positions at which drivers arepotentially located that have the highest frequencies are ranked andidentified as the most best candidates for ablation.

In some instances, a further stage may occur after stage 1710 in whichone or more rankings are mapped to a representation of the heart. Forexample, a three-dimensional image or model of the heart may be markedwith a color or other indicator to identify a potential driver, ortarget site for ablation. If multiple drivers are identified, with onedriver having a higher frequency and one or more further drivers havinga lower frequency, such that the higher frequency driver may have ahigher likelihood of being a primary driver, the marking oridentification may proceed in a manner to distinguish the variousdrivers from one another. For example, the higher frequency driver maybe marked with a color or otherwise identified in a manner thatsignifies that the position on the heart is likely a driver and is thusa good candidate for ablation, and the one or more lower frequencypositions may be identified as less likely positions at which a primarydriver is located. Even where only a single potential driver isidentified, a similar identification may take place. For example, insome instances, it may be determined that any potential driver having afrequency that is above a threshold value (e.g., having a period of nogreater than 100 milliseconds, in some instances) is a good candidatefor ablation and thus may be identified accordingly (e.g., by marking athree-dimensional map with a specific color or other indicator). Otherthresholds may also be determined. For example, potential positions thatexhibit periods at or below a lower threshold may be identified as gooddriver candidates, positions that exhibit periods between the lowerthreshold and an upper threshold may be identified as fair drivercandidates, and positions that exhibit periods at or above the upperthreshold may be identified as poor driver candidates. Other rankingvalues and identification systems are also contemplated.

At stage 1712, the highest and/or higher ranked probable atrial driverelectrograms are located and focal ablation is performed at one or moreof the locations. The location may be determined from a map of theheart, which may be directly correlated to the various positions fromwhich the electrograms are gathered, in manners such as discussed above.

At stage 1714, it is determined whether atrial fibrillation has beenresolved. If so, then the method is at an end at stage 1716. If not, themethod proceeds to stage 1730 to determine whether the atrialfibrillation, though not resolved, has at least changed. If there hasbeen a change, then the method loops back to stage 1712 again. However,if there has been no change, then the method proceeds to stage 1722. Insome instances, after an evaluation is made at stage 1714,reconsideration may be made in the setting of isopenaline(isoprotenenol, or “Isuprel”).

Reference is again made to stage 1720, the completion of which alsoresults in progression to the stage 1722. At stage 1720, if the decisionat stage 1706 is negative, then the local electrogram is identified as aprobably secondary driver. Reassessment of whether a probable secondarydriver is in fact a primary driver occurs at stage 1722. If it isdetermined that what was originally considered to be a secondary drivermay in fact be a primary driver, then the method can loop back again tostage 1708.

Referring again to stage 1704, if no local electrograms demonstratestable frequencies, then the method can proceed to stage 1742, at whichit is determined whether any local electrograms have intermittentsuppression of a stable frequency, or stated otherwise, whether theelectrogram would have a stable frequency, but for the existence ofintermittent suppression of expected signals or wavefronts at theotherwise stable frequency. If such suppression is or appears to bepresent (e.g., suppression such as shown in FIG. 34B or 35B), then themethod proceeds to stage 1744. If not, then the method proceeds to stage1750, at which the electrogram substrate locations are identified asunlikely atrial driver sites. The identification can include the markingof a three-dimensional model of the heart in manners such as discussedabove.

At stage 1744, it is determined whether the local electrogram returns tothe original, regular frequency after suppression. If so, then themethod cycles back to stage 1706. If not, then the method cycles back tostage 1750. After arriving at stage 1750, a sensor may be repositionedto a new area of the heart wall (e.g., for some contact sensors), or anew sensing region may be identified (e.g., for other, larger-areacontact sensors and/or non-contact sensors that sense over a largeregion). The method 1700 may then be repeated at the new region of theheart.

The method 1700 can be repeated as treatment progresses. For instance,as an atrial driver location is treated by ablating the cardiac tissueassociated with the targeted site, newly acquired sensor data can beacquired and then used to assess the substrate for other probable atrialdriver targets.

As with other methods herein, one or more of the stages may be performedby a computer or other specialized equipment. For example, any suitableprogram that implements algorithms such as described herein iscontemplated. Moreover, any suitable subset of stages may constitute aseparation method. By way of example, some methods may comprise stages1702, 1704, 1706, and 1708; further methods may additionally comprisestage 1710; and further methods still may additionally comprise stage1712. Some methods may comprise stages 1702, 1704, 1742, 1744, 1706,1708, and/or 1710; and further methods may additionally comprise stage1712.

FIG. 42 is a flowchart depicting another method of treating atrialfibrillation. The method closely resembles the method 1800. Inparticular, the stages 1804, 1806, 1808, 1810, 1812, 1814, 1820, 1822,1830, 1842, 1844, and 1850 can be the same as the stages 1804, 1706,1708, 1710, 1712, 1714, 1720, 1722, 1730, 1742, 1744, and 1750. However,the method further includes the stages 1803 and 1840. Any suitablesubset of the foregoing steps is also contemplated.

The step 1803 resembles the step 1702 discussed above, but furtherincludes acquisition of near field electrograms from the substrate. Thecollection of the near field and local electrograms can be simultaneousor substantially simultaneous, and may be performed in any suitablemanner. The term “near field electrogram” is meant in its ordinarysense.

The method proceeds from stage 1804 to stage 1840 if it is determinedthat no local electrograms have stable frequencies. If this is the case,then it is determined whether any near field electrograms have stablefrequencies. If so, then the method proceeds to stage 1806. If not, thenthe method proceeds to stage 1842. Accordingly the stage 1840 canprovide another indication that stable frequencies exist relative to aregion of the heart.

Either of the methods 1700, 1800 can be combined with other methodsdisclosed herein to identify and/or isolate drivers. For example, insome methods that include at least some of the stages of the methods1700, 1800 can further include some or all of the stage of the methods200, 240, 260, 700. For example, ranking algorithms that weigh thefrequency, regularity (or stability), etc. of electrograms, wavefronts,and/or wavefront patterns may be used before, after, or otherwise inconjunction with any suitable stage or stages of the methods 1700, 1800.By way of illustrative example, the stages 702, 704, 706, and 708 of themethod 700 may be performed in conjunction with the stages 1702, 1803 ofthe methods 1700, 1800, and the stage 710 may be performed inconjunction with (e.g., before, after, or simultaneously with) the stage1710, 1810 of the methods 1700, 1800.

FIG. 43 is a plan view of an embodiment of a sensor assembly 2000 in theprocess of gathering electrograms from a portion of an atrial wall 2050,wherein a driver 2030 is within a sensing region of the sensor assembly2050. The sensor assembly 2000 can be of any suitable variety. In theillustrated embodiment, the sensor assembly 2000 includes five separateindividual support structures or branches 2004 that radiate from adistal end of a catheter 2006. In certain embodiments, the branches 2004can be flexible so as to be able to readily move into contact with theatrial wall 2050. Accordingly, although the branches 2004 areconsistently illustrated in the drawings as being equally spaced fromone another in FIG. 43 and in subsequent drawings, the branches 2004need not necessarily assume such a symmetrical configuration, in someembodiments. For example, in some arrangements, some or all of thebranches 2004 may be closer to each other and/or some or all of thebranches 2004 may be spaced further apart from each other than what isdepicted in the illustrative drawings. In some embodiments, the sensorassembly 2000 can be configured to detect or otherwise provideinformation regarding the relative orientations of the branches 2004such that information regarding the direction in which each branch ispointed and/or the location of each sensor 2002 is known. In someembodiments, the sensor assembly 2000, the sensor assembly 2000 cancomprise a PentaRay® NAV Catheter.

Each branch 2004 of the sensor assembly can include a plurality ofsensors 2002. Only one of the sensors 2002 is identified by thereference numeral “2002,” but each of the sensors is identified in thedrawings by its sensor number—S1, S2, S3, S4, S5, S6, S7, S8, S9, S10,S11, S12, S13, S14, S15, S16, S17, S18, S19, S20. In some instances, thesensor assembly 2000 may operate in a unipolar mode in which each of thesensors 2002 detects a potential relative to a common reference voltage.In other instances, the sensor assembly 2000 may operate in a bipolarmode in which sets of adjacent sensors 2002 measure relative potentialdifferences between the sensors. For example, in the illustratedembodiment, when the sensor assembly is operating in the bipolar mode,potential differences between adjacent sets of sensors that arepositioned along the same branch are measured. Thus, for example,potential differences between the sensors S13 and S14, between S14 andS15, and between S15 and S16 may be obtained along one branch, and eachset of adjacent sensors may thus observe the electrical activity ofspecific regions 2081, 2082, 2083, respectively, of the atrial wall2050.

The positioning catheter 2006 may be used to move the distal head of thesensor assembly 2000 to a desired location along the atrial wall 2050.This is depicted by the arrow 2001. In some procedures, the sensorassembly 2000 may be used to map and/or measure electrical activityalong a large portion of the atrial wall 2050. In some instances, asubstantial portion of the atrial wall 2050 may be observed or measuredduring the course of a procedure.

In some procedures, the distal head of the sensor assembly 2000 may bemoved to a desired position and one or more of the branches 2004 may bemoved into electrical contact with the atrial wall 2050. The sensorassembly 2000 may then be held in place for a sufficient time to take adesired set of measurements. In various instances, the sensor assembly2000 may be held substantially stationary relative to the atrial wallfor a period of up to about 200, 400, 600, or 800 milliseconds. In otherinstances, an observation period may be one or more seconds, or may lastfor up to one, two, or three heartbeats. In some instances, the sensorassembly 2000 may be held in place for up to a minute as measurementsare gathered. After a desired set of data is obtained, the sensorassembly 2000 may be moved to another portion of the atrial wall 2050.

FIG. 43 represents a situation in which a driver 2030 is within asensing region of the sensor assembly 2000 during an observation event.The driver 2030 regularly propagates wavefronts 2051, 2052, 2053outwardly in manners such as discussed above. Electrograms obtained bythe sensors 2004 may be used to determine the approximate and/or exactlocation of the driver 2030, as discussed hereafter.

FIG. 44A is a plot 2100 that includes electrograms gathered via thesensor assembly 2000 and that also shows a base signal 2102 of theheart. The electrogram obtained via the sensors S1 and S2 is designatedDD 1-2, the electrogram obtained via the sensors S2 and S3 is designatedDD 2-3, and so on. In the illustrated plot, the electrograms arearranged in ascending order of the sensor number. However, as can beseen in FIG. 44A, such an ordering of the electrograms does notnecessarily or always readily reveal a pattern, such as wavefrontpropagation. It thus may be desirable to rank, sort, rearrange, orotherwise evaluate the electrograms and obtain information that may beused to determine an approximate or exact location of the driver 2030.

In some embodiments, a program implemented by a general purpose computeror dedicated hardware may evaluate and/or rank the electrograms based onone or more properties, such as, for example, waveform unity, frequency,amplitude, shape (e.g., slope, initial direction—whether positive ornegative, sharpness, number of peaks or valleys, etc.). Timing may alsobe a key property used in ranking or sorting the electrograms, and insome instances, earlier presence of a wavefront will receive a higherranking.

The result of such a ranking algorithm is shown in the plot 2105 in FIG.44B, in which the highest ranked electrogram is listed first, the nexthighest is listed second, and so on. Whereas in some procedures, theranking is performed by a computer or is otherwise automated, in otherprocedures, the ranking may be done visually by a practitioner. In otheror further instances, the ranking may involve some form of manipulationof the electrograms by a practitioner, such as by dragging and droppingor some other movement using, for example, peripheral computer controlsor a touchscreen. Thus, a practitioner might also be capable ofrearranging, sorting, or ranking the electrograms into the order shownin FIG. 44B.

As mentioned above, the frequency (or period) of the electrograms canfactor into a ranking algorithm. For example, the shorter the periodbetween successive wavefronts, the higher the weighting an electrogrammay receive. Thus, it may be desirable for the shortest periodelectrograms to appear at the top of the plot 2105, which can aid indetermining the location of a target portion of the atrial wall 2050 atwhich a primary driver is expected to be located. In the illustratedembodiment, the period t₁ between successive wavefronts is shown.

Based on the observation or calculation that wavefronts first appear inthe region between the sensors S19 and S20 and then propagate away fromthis region, it can be determined that the target region is closest tothat region of the cardiac wall 2050. In some instances, the regionbetween S19 and S20 is treated as a sufficiently close approximation asto the location of the driver 2030. Accordingly, the procedure mayidentify that location as the target spot.

In other embodiments, further calculations or observations can beconducted to conclude that the target area, although close to theposition between the sensors S19 and S20, is actually between thebranches that include the sensors S17, S18, S19, S20 and the sensors S1,S2, S3, and S4. Thus an even closer approximation may be obtained bymaking the target area somewhere between the positions between thesensors S19 and S20 and the sensors S3 and S4. Further algorithms may beused to even more accurately interpolate the position of the driver2030. The algorithms may take into account such factors as the relativepositions of the branches of the sensor assembly 2000, the relativepositions of the sensors 2002, the differences in time at whichwavefronts reach the respective sensor regions, etc.

In the illustrated embodiment, a single driver 2030 is identified. Insome instances, signals from the driver 2030 might appear at each of thesensing regions, such that the propagation of the wavefronts will beeven more apparent than what is shown in FIG. 44B. However, as can beseen in FIG. 44B, no every sensing region has received a signal from thedriver 2030. This can be due to one or more of a variety of reasons,such as poor sensor contact with the atrial wall 2050, contact with anarea of the wall that is non-electrically conductive (e.g., due to aprior ablation), etc.

Once a target position for the driver 2030 has been determined, thisposition can be identified on a map or plot (e.g., a representativeimage, such as the image 191 discussed above) of the heart. In someinstances, the identification can be used for subsequent ablation. Forexample, in some instances, detection of different driver positionstakes place over a period of time, and once all such desired positionshave been identified, focal ablation of specific positions that have thehighest ranking, or likelihood of being primary drivers, then proceeds.

The identification may be of any suitable variety. For example, asdiscussed above, the identification may take the form of adding color tothe three-dimensional plot. In some instances, three different colorsmay be used to identify driver regions of fast, medium, or slowfrequencies, which may correlate with high, intermediate, and lowlikelihood of being primary drivers. Further discussion ofidentification procedures are provided above. In some instances, after adesired number of such driver positions have been identified, theablation may then proceed, and in some instances, only the most likelycandidates for primary drivers are ablated. Other systems foridentifying and ablating are contemplated. Additionally, in variousinstances, the periods for what are considered fast, medium, and slowdrivers may vary, such as from patient to patient. Accordingly, in someinstances, the thresholds for what is fast, medium, or slow may be setaccording to a relative scale, as determined by the physiology of thepatient.

FIG. 45 is a plan view of the sensor assembly 2000 in the process ofgathering electrograms from another portion of the atrial wall 2050,wherein two separate drivers 2230, 2231 are within a sensing region ofthe sensor assembly. For example, the information gathering that istaking place in FIG. 45 can occur at a later time during theidentification of possible drivers and prior to a focal ablationprocedure. The driver 2230 provides wavefronts (e.g., 2251, 2252, 2253)at a higher frequency than the driver 2231 provides wavefronts (e.g.,2261, 2262, 2263).

FIG. 46A is a plot 2300 that includes electrograms gathered via thesensor assembly 2000 and that also shows a base signal of the heart.Calipers (as shown by dashed vertical lines) may be provided to assist apractitioner in identifying a minimum period from among theelectrograms, as well as an electrogram for which wavefronts appearfirst and then propagate onward to other sensed regions. In somearrangements, the calipers may be used instead of or in addition tosorting or rearranging the electrograms in the vertical dimension.

Such a sorting or ranking is shown in FIG. 46B. In the illustratedembodiments, the two drivers within the sensing area generate uniquewaveforms having nearly the same period, although the driver 2230 has ashorter period. In the illustrated sorting algorithm, the electrogramsassociated with the driver 2230 are higher along the vertical axis than,or stated otherwise, are ranked above, the electrograms that areassociated with the driver 2231. This may result from the higherfrequency of the driver 2230.

In some instances, a sorting algorithm may take into account variousproperties of the waveforms to conclude that multiple drivers are beingsensed. For example, the two sets of waveforms have different overallshapes. The higher frequency waveform initiates with a small dip andthen a large peak, for example, whereas the lower frequency waveforminitiates with a small peak and then a large dip.

The plot 2305 shows multiple interacting drivers of distinct morphologyand frequency. In DD 13-14, DD 14-15, a slow repetitive driver is notedby morphology and frequency with a simultaneous much more rapid,repetitive driver that has a distinct morphology and frequency.

As with identifying individual drivers, the target locations may beestimated approximately, or may be interpolated or otherwise calculatedwith a higher degree of accuracy. For example, in some procedures, oneor more of the regions that are at or close to the regions between thesensors 10 and 11 and between the sensors 2 and 3 may be targeted, asthe separate waveforms appear to generally propagate away from theseregions.

FIG. 47 is a plan view of an embodiment of the sensor assembly 2000 inthe process of gathering electrograms from another portion of the atrialwall 2050, wherein a driver 2430 is external to a sensing region of thesensor assembly. FIG. 48A is a plot that includes electrograms gatheredvia the sensor and that also shows a base signal of the heart. FIG. 48Bis a plot that includes the electrograms from FIG. 48A in a sorted orrearranged format to demonstrate propagation of wavefronts from thedriver.

In some embodiments, an algorithm may be used to determine that thedriver 2430 is not between any of the branches of the sensor assembly2000. Such algorithms may utilize time delay, sensor position, and/orother properties or variables of the sensed waves to determine anapproximate or estimated location of the driver 2430. In other orfurther embodiments, the algorithm may provide a suggested direction formoving the distal end of the sensor assembly 2000 in order to bring thedriver 2430 within the sensing area of the sensor assembly 2000 anddetermine more accurately the position of the driver 2430. In someembodiments, the suggested direction may occur on a display of themapped heart. For example, the suggested direction may be depicted by anarrow or some other indicator on a display, which a practitioner canthus visualize and respond to in order to move the sensor assembly 2000.

FIG. 49 is a plan view of the sensor assembly 2000 in the process ofgathering electrograms from another portion of the atrial wall 2050,wherein a first driver 2630 is at an exterior of the sensing region ofthe sensor assembly 2000 and a second driver 2631 is within the sensingregion of the sensor assembly 2000. FIG. 50A is a plot that includeselectrograms gathered via the sensor assembly 2000 and that also shows abase signal of the heart. FIG. 50B is a plot that includes theelectrograms from FIG. 50A in a ranked or rearranged format todemonstrate propagation of wavefronts from the drivers. Ranking orsorting of the waveforms, identification of target sites, and otherprocedures relative to the various sensed drivers can proceed in mannerssuch as described above, particularly with respect to FIGS. 43-48B.

FIG. 51 is a plan view of the sensor assembly 2000 in the process ofgathering electrograms from another portion of the atrial wall 2050,wherein two drivers 2830, 2831 are near a sensing region of the sensorassembly, but are outside of the sensing region. FIG. 52A is a plot thatincludes electrograms gathered via the sensor and that also shows a basesignal of the heart. FIG. 52B is a plot that includes the electrogramsfrom FIG. 52A in a rearranged format to demonstrate propagation ofwavefronts from the drivers. Ranking or sorting of the waveforms,identification of target sites, and other procedures relative to thevarious sensed drivers can proceed in manners such as described above,particularly with respect to FIGS. 47-50B.

FIG. 53 is a plan view of an embodiment of a sensor assembly in theprocess of gathering electrograms from the same portion of the atrialwall 2050 that is shown in FIG. 51. The atrial wall 2050 is shown afteran ablative procedure has been conducted to cease activity of the driver2831. FIG. 54A is a plot that includes electrograms gathered via thesensor and that also shows a base signal of the heart. FIG. 54B is aplot that includes the electrograms from FIG. 54A in a rearranged formatto demonstrate propagation of wavefronts from the driver 2830. Due tothe continued presence of a driver, a further ablative procedure may bedesired. It is noted that the driver 2831 shown in FIG. 51 had a lowerfrequency than the driver 2830, although their frequencies were aboutthe same. As discussed above, however, in many instances, the driverswith the higher or highest frequencies will be ablated in a preliminaryablation procedure.

Any methods disclosed herein comprise one or more steps or actions forperforming the described method. The method steps and/or actions may beinterchanged with one another. In other words, unless a specific orderof steps or actions is required for proper operation of the embodiment,the order and/or use of specific steps and/or actions may be modified.Moreover, sub routines or only a portion of a method illustrated in thedrawings, such as a small subset of step, may be a separate method.Stated otherwise, some additional methods may include only a portion ofthe steps shown in a more detailed method.

References to approximations are made throughout this specification,such as by use of the terms “about” or “approximately.” For each suchreference, it is to be understood that, in some embodiments, the value,feature, or characteristic may be specified without approximation. Forexample, where qualifiers such as “about,” “substantially,” and“generally” are used, these terms include within their scope thequalified words in the absence of their qualifiers.

Reference throughout this specification to “an embodiment” or “theembodiment” means that a particular feature, structure or characteristicdescribed in connection with that embodiment is included in at least oneembodiment. Thus, the quoted phrases, or variations thereof, as recitedthroughout this specification are not necessarily all referring to thesame embodiment.

Similarly, it should be appreciated that in the above description ofembodiments, various features are sometimes grouped together in a singleembodiment, figure, or description thereof for the purpose ofstreamlining the disclosure. This method of disclosure, however, is notto be interpreted as reflecting an intention that any claim require morefeatures than those expressly recited in that claim. Rather, as thefollowing claims reflect, inventive aspects lie in a combination offewer than all features of any single foregoing disclosed embodiment.

The claims following this written disclosure are hereby expresslyincorporated into the present written disclosure, with each claimstanding on its own as a separate embodiment. This disclosure includesall permutations of the independent claims with their dependent claims.Moreover, additional embodiments capable of derivation from theindependent and dependent claims that follow are also expresslyincorporated into the present written description.

Recitation in the claims of the term “first” with respect to a featureor element does not necessarily imply the existence of a second oradditional such feature or element. Elements specifically recited inmeans-plus-function format, if any, are intended to be construed inaccordance with 35 U.S.C. §112 ¶ 6. Embodiments of the invention inwhich an exclusive property or privilege is claimed are defined asfollows.

1-44. (canceled)
 45. A method of treating cardiac complex rhythmdisorder in a patient, the method comprising: receiving a plurality ofelectrical signals from a sensor system, wherein each electrical signalcorresponds with a separate location on a cardiac wall of the heart ofthe patient, wherein each electrical signal comprises an electrogramwaveform, and wherein at least some of the plurality of electricalsignals comprise first wavefronts that are distinguishable from a basesignal of the heart; ranking the plurality of electrical signalsrelative to each other by: determining that at least some of theelectrogram waveforms show propagation of the first wavefronts;assigning a higher ranking to an electrical signal in which the firstwavefronts are present at an earlier time, as compared with a ranking ofan electrical signal in which the first wavefronts are present at alater time; and if an electrical signal has an electrogram waveform thathas a stable frequency that is higher than a stable frequency of anotherelectrogram waveform of another electrical signal, assigning a higherranking to the electrical signal that is associated with the higherfrequency as compared with a ranking of the electrical signal that isassociated with the lower frequency; and identifying a target site ofthe cardiac wall for ablation based on the ranking of the electricalsignals.
 46. The method of claim 45, further comprising: determiningthat a particular electrical signal comprises an electrogram waveformhaving a stable frequency that is intermittently suppressed; anddetermining that the electrogram waveform of the particular electricalsignal returns to the stable frequency after intermittent suppression,wherein identifying the target site comprises identifying the locationon the cardiac wall that corresponds with the particular electricalsignal.
 47. The method of claim 45, wherein identifying the target sitecomprises interpolating a location of the target site from locations onthe cardiac wall that correspond with at least some of the electricalsignals that have been ranked.
 48. The method of claim 45, wherein someof the plurality of electrical signals comprise second wavefronts thatare distinguishable from the base signal of the heart, wherein the firstwavefronts occur at a first stable frequency, wherein the secondwavefronts occur at a second stable frequency that is lower than thefirst stable frequency, and wherein ranking the electrical signalsrelative to each other comprises assigning electrical signals thatcomprise the first wavefronts a higher ranking than electrical signalsthat comprise the second wavefronts.
 49. The method of claim 45, furthercomprising receiving a plurality of additional electrical signals fromthe sensor system after the sensor system has been relocated relative tothe cardiac wall of the heart, wherein each additional electrical signalcorresponds with a separate location on a cardiac wall of the heart ofthe patient, wherein each additional electrical signal comprises anelectrogram waveform, and wherein at least some of the plurality ofadditional electrical signals comprise second wavefronts that aredistinguishable from the base signal of the heart; ranking the pluralityof additional electrical signals relative to each other by: determiningthat at least some of the electrogram waveforms of the additionalelectrical signals show propagation of the second wavefronts; andassigning a higher ranking to an additional electrical signal in whichthe second wavefronts are present at an earlier time, as compared with aranking of an additional electrical signal in which the secondwavefronts are present at a later time; and identifying an additionaltarget site of the cardiac wall for ablation based on the ranking of theadditional electrical signals.
 50. The method of claim 45, wherein thetarget site corresponds with a location on the cardiac wall thatcorresponds with an electrical signal that receives a higher rankingthan do other electrical signals.
 51. The method of claim 50, whereinthe target site corresponds with a location on the cardiac wall thatcorresponds with an electrical signal that receives the highest ranking.52. The method of claim 45, wherein the sensor system simultaneouslyacquires the plurality of electrical signals from different portions ofa surface within the heart that extends in at least two dimensions. 53.The method of claim 45, wherein the plurality of sensors are interior toa wall of a heart of the patient and are spaced from the wall so as notto contact the wall while the heart is beating.
 54. The method of claim45, wherein electrical signals transmitting from the pulmonary veins areisolated from the cardiac wall via tissue ablation prior to receivingthe plurality of electrical signals from the sensor system.
 55. Themethod of claim 45, wherein ranking the plurality of electrical signalsrelative to each other comprises assigning a higher ranking to anelectrical signal that has a greater uniformity, as compared with aranking of an electrical signal that has a lesser uniformity.
 56. Themethod of claim 45, further comprising: generating a representativeimage of the heart of the patient; and identifying one or more targetpositions on the representative image that correspond with one or morelocations on the cardiac wall that correspond with as one or moreelectrical signals, respectively, that receive higher rankings than doother electrical signals.
 57. The method of claim 45, wherein theplurality of electrical signals are received from a sensor system onto acomputing device, wherein ranking the plurality of electrical signals isachieved via the computing device, and wherein identifying the targetsite is achieved via the computing device.
 58. The method of claim 46,wherein the plurality of electrical signals are received from a sensorsystem onto a computing device, and wherein each of ranking theplurality of electrical signals, identifying the target site,determining that the particular electrical signal comprises anelectrogram waveform having a stable frequency that is intermittentlysuppressed, and determining that the electrogram waveform of theparticular electrical signal returns to the stable frequency afterintermittent suppression are achieved via the computing device.
 59. Amethod of treating cardiac complex rhythm disorder in a patient, themethod comprising: receiving a plurality of electrical signals from asensor system that senses a region of a cardiac wall of the patient,wherein each electrical signal corresponds with a separate locationwithin the region of the cardiac wall of the patient, and wherein eachelectrical signal comprises an electrogram waveform; determining thatthe electrogram waveforms include electrical wavefronts that aredistinguishable from a base signal of the heart and that the electrogramwaveforms show propagation of the electrical wavefronts away from atleast a portion of the region of the cardiac wall; ranking the separatelocations on the cardiac wall as to their likelihood of being the siteof an atrial driver by comparing the electrogram waveforms based on thetiming at which the electrical wavefronts are present; and determiningthat the electrical wavefronts occur at a stable frequency.
 60. Themethod of claim 59, wherein determining that the electrical wavefrontsoccur at a stable frequency comprises determining the stable frequencydespite intermittent suppression of the electrical wavefronts.
 61. Themethod of claim 59, wherein the sensor system is positioned within aheart of the patient
 62. The method of claim 59, wherein a location onthe cardiac wall at which the electrical wavefronts are first presentreceives a higher ranking, as compared to at least some of the remainingseparate locations on the cardiac wall.
 63. The method of claim 62,wherein a location on the cardiac wall at which the electrical wavefrontis first present receives the highest ranking of separate locations onthe cardiac wall at which the wavefront is present at any time.
 64. Themethod of claim 59, wherein electrical signals transmitting from thepulmonary veins are isolated from the cardiac wall via tissue ablationprior to receiving the plurality of electrical signals from the sensorsystem.
 65. The method of claim 59, further comprising identifying atarget site of the cardiac wall based on the ranking of the electricalsignals, wherein the target site corresponds with a location on thecardiac wall that corresponds with an electrical signal that receives ahigher ranking, as compared to at least some of the remaining electricalsignals that correspond with separate locations on the cardiac wall. 66.The method of claim 59, further comprising: generating a representativeimage of the heart of the patient; and identifying a target position onthe representative image that corresponds with the location on thecardiac wall that corresponds with an electrical signal that receives ahigher ranking, as compared to at least some of the remaining separatelocations on the cardiac wall.
 67. A method of treating cardiac complexrhythm disorder in a patient, the method comprising: receiving anelectrical signal from a sensor system, wherein the electrical signalcorresponds with a location on a cardiac wall of the heart of thepatient, and wherein the electrical signal comprises an electrogramwaveform; determining whether the electrogram waveform showsintermittent suppression of a stable frequency; determining whether theelectrogram waveform returns to the stable frequency after thesuppression; and identifying the location on the cardiac wall as atarget for focal ablation.
 68. The method of claim 67, furthercomprising receiving a plurality of electrical signals from the sensorsystem, wherein each electrical signal corresponds with a separatelocation on a cardiac wall of the heart of the patient, and wherein theelectrical signal comprises an electrogram waveform; determining whetherthe electrogram waveforms show propagation of an electrical wavefront;and ranking the separate locations on the cardiac wall as to theirlikelihood of being the site of an atrial driver by comparing theelectrogram waveforms based on the timing at which the electricalwavefront is present therein.